Here is a suggested solution:

// Formats numbers with commas.
String.prototype.commafy = function()
{
    return this.replace(/ (^|[^\w.])(\d{ 4,})/ g, function($0, $1, $2) {
        return $1 + $2.replace(/\d(?= (?:\d\d\d) + (? !\d))/ g, "$&,");
    });
};

/**
 * Rounds decimals.
 * @param {number} num - The number to round...
 * @param {number} scale - How many decimal places?
 */
function fixed (num, scale) {
  return (+(Math.round(+(num + "e" + scale)) + "e" + -scale)).toFixed(scale);
}

// Declare variables
var totalCap;
var totalCapTemp;
var bitcoinPriceTemp;
var bccPriceTemp;
var bitcoinMarketCap;
var bccMarketCap;
var bitcoinMarketCapTemp;
var bccMarketCapTemp;
var bitcoinMarketShareTemp;
var bccMarketShareTemp;
var bitcoinMarketShare;
var bccMarketShare;
var bitcoinVolTemp;
var bccVolTemp;
var bitcoinChangeTemp;
var bccChangeTemp;
var bitcoinTxTemp;

var chart;
var myVar = setInterval(myTimer, 60000);

// When document is ready
$(document).ready(function() {
    myTimer();
});

// Function to run in order
function runInOrder(callback)
{
    getTotalMarketCap(function() {
        getAllOtherValues(function() {
            getMarketShare(callback);
        });
});
}

// Get total market cap
function getTotalMarketCap(callback)
{
    $.getJSON("https://api.coinmarketcap.com/v1/global/", function(json) {
        // Processing data
        totalCap = fixed (parseFloat(json.total_market_cap_usd / 1000000000), 2);
        // Display data on the page
        if (!totalCapTemp || totalCapTemp == totalCap)
        {
            $("#totalCap")
            .text("$" + totalCap + "B")
            .removeClass();
        }
        else if (totalCap > totalCapTemp)
        {
            $("#totalCap")
            .text("$" + totalCap + "B")
            .removeClass()
            .addClass("green");
        }
        else
        {
            $("#totalCap")
            .text("$" + totalCap + "B")
            .removeClass()
            .addClass("red");
        }
        totalCapTemp = totalCap;
        callback();
    });

}

// Get all other values
function getAllOtherValues(callback)
{
    // Process data
    var lastInstruction = function(){
    // Get data from API
    $.getJSON("https://api.blockchain.info/stats?cors=true", function(json) {
            // Process Bitcoin transactions
            bitcoinTx = json.n_tx.toLocaleString();
            // Display Bitcoin transactions
            if (!bitcoinTxTemp || bitcoinTxTemp == bitcoinTx)
            {
                $("#bitcoinTx")
                .text(bitcoinTx)
                .removeClass();
            }
            else if (parseInt(bitcoinTx) > parseInt(bitcoinTxTemp))
            {
                $("#bitcoinTx")
                .text(bitcoinTx)
                .removeClass()
                .addClass("green");
            }
            else
            {
                $("#bitcoinTx")
                .text(bitcoinTx)
                .removeClass()
                .addClass("red");
            }
            bitcoinTxTemp = bitcoinTx;
            callback();
        });
    };

    // Get data from API
    $.getJSON("https://api.coinmarketcap.com/v1/ticker/?limit=10", function(
        json
    ) {
        // Process data for Bitcoin and Bitcoin Cash
        // Display data on the page
        $.each(json, function(index, value) {
            if (value.id == "bitcoin")
            {
                // Bitcoin processing
            }

            if (value.id == "bitcoin-cash")
            {
                // Bitcoin Cash processing
            }

            if (index >= json.length - 1)
                lastInstruction();

        });
    });


}

// Get market share
function getMarketShare(callback)
{
    // Calculate Bitcoin market share
    // Display Bitcoin market share on the page
    // Update chart if needed

    // Calculate Bitcoin Cash market share
    // Display Bitcoin Cash market share on the page
    // Update chart if needed

    callback && callback();
}

// Create chart
function createChart()
{
    $(function() {
        Chart.defaults.global.legend.display = false;
        Chart.defaults.global.animation.duration = 0;
        var ctx = document.getElementById("myChart").getContext("2d");
        $("#myChart").css("background-color", "#222428");

        // Create a doughnut chart
        chart = new Chart(ctx, {
            type: "doughnut",
            data: {
                labels: ["Bitcoin", "Bitcoin Cash", "Others"],
                datasets: [
                    {
                        label: "dataset",
                        backgroundColor: ["#2196f3", "#f44336", "#FFFFFF"],
                        borderColor: "#000000",
                        data: [
                          bitcoinMarketShare,
                          bccMarketShare,
                          fixed (100 - bccMarketShare - bitcoinMarketShare, 2)
                        ]
                    }
                ]
            },
            options:
                {
                    cutoutPercentage: 70,
                    rotation: 185
                }
        });
    });
}

Make sure to call the callback inside $.getJSON's success handler