Keeping a tally of INPUT contents

Given a set of inputs, keep a running total as dollars of all numbers within them.

HTML

<input type="text" class="test" id="lineAmount"></input><br>
<input type="text" class="test" id="lineAmount"></input><br>

<hr>
<input type="textbox" id="DepositSum">
<div id="para"></div>

JavaScript

function formatNumber(myStr) {
    myStr = myStr.toString().replace(/\$|\,/g, '');
    return myStr;
}

function formatCurrency(num) {
    num = num.toString().replace(/\$|\,/g, '');
    if (isNaN(num)) num = "0";
    sign = (num == (num = Math.abs(num)));
    num = Math.floor(num * 100 + 0.50000000001);
    cents = num % 100;
    num = Math.floor(num / 100).toString();
    if (cents < 10) cents = "0" + cents;
    for (var i = 0; i < Math.floor((num.length - (1 + i)) / 3); i++)
    num = num.substring(0, num.length - (4 * i + 3)) + ',' + num.substring(num.length - (4 * i + 3));
    if (num == "0") {
        return (" ");
    } else {
        return (((sign) ? '' : '-') + '$' + num + '.' + cents);
    }
}


$(".test").keyup(function (e) {
    var add = 0;
    $('.test').each(function () {
        tmpVal = $(this).val().toString().replace(/\$|\,/g, '');
        if (isNaN(tmpVal) == false) {
            add += Number(tmpVal);
        }
    });
    $("#para").text("Sum of all textboxes is : " + formatCurrency(add));
    $("#DepositSum").val(formatCurrency(add));
});

$(".test").blur(function () {
    $(this).val(formatCurrency($(this).val()));
});
$(".test").focus(function () {
    $(this).val(formatNumber($(this).val()));
});