As you might know, jQuery and Mootools can exist in the same page, anyway to answer your question, try this:
aVariable: function (elems, locks, hiddenInput, elem) {
initialValue = '';
var round = function (inputValue, precision) {
precision = Math.pow(10, precision || 0).toFixed(precision < 0 ? -precision : 0);
return Math.round(inputValue * precision) / precision;
}
if (elem) {
var val = round(parseFloat(elem.value),2);
var v = val ? val : '0';
elem.value = v;
Serialize.verifyInput(elems, elem, locks);
}
}