Firefox-input-selector.js

// Grabs the size selected and adds it to the total
$("select[name = 'sizes[]']").click(function(){
	var sizes = $("select[name = 'sizes[]']");
	var counter = 0;
	for (var i=0; i < sizes.length; i++) {
		counter = Number(counter) + Number(sizes[i].value);
		};
				
	sub_total = counter;
					
	$("#sub_total").text("$" + sub_total + ".00");
	});

Webkit-input-selector.js

// Grabs the size selected and adds it to the total
$("select").change(function(){
        var sizes = $("select[name = 'sizes[]']");
        var counter = 0;
	for (var i=0; i < sizes.length; i++) {

	counter = Number(counter) + Number(sizes[i].value);
	};

	sub_total = counter;

	$("#sub_total").text("$" + sub_total + ".00");
	});