How get sum of total values in stackedBar ChartJs

First you should know that if you return an array instead of a single string in the callback of the tooltip, it will display all the strings in your array as if it were different datasets (see this answer for more details).

So I edited a little bit your callback to the following:

callbacks: {
    label: function(tooltipItem, data) {
        var corporation = data.datasets[tooltipItem.datasetIndex].label;
        var valor = data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index];

        // Loop through all datasets to get the actual total of the index
        var total = 0;
        for (var i = 0; i < data.datasets.length; i++)
            total += data.datasets[i].data[tooltipItem.index];

        // If it is not the last dataset, you display it as you usually do
        if (tooltipItem.datasetIndex != data.datasets.length - 1) {
            return corporation + " : $" + valor.toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,');
        } else { // .. else, you display the dataset and the total, using an array
            return [corporation + " : $" + valor.toFixed(2).replace(/(\d)(?=(\d{3})+\.)/g, '$1,'), "Total : $" + total];
        }
    }
}

You can see the full code in this jsFiddle, and here is its result :

i modified tektiv answer to show Total only for active sets and move it to tooltips footer.

tooltips: {
        mode: 'label',
        callbacks: {
            afterTitle: function() {
                window.total = 0;
            },
            label: function(tooltipItem, data) {
                var corporation = data.datasets[tooltipItem.datasetIndex].label;
                var valor = data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index];
                window.total += valor;
                return corporation + ": " + valor.toString().replace(/\B(?=(\d{3})+(?!\d))/g, " ");             
            },
            footer: function() {
                return "TOTAL: " + window.total.toString().replace(/\B(?=(\d{3})+(?!\d))/g, " ");
            }
        }
    }