You can try this (untested)
//BEGIN
var num = ((igedit_getById('txtNewWage').text.replace(',', '') - igedit_getById('txtCurrentWage').text.replace(',', '')) /
igedit_getById('txtCurrentWage').text.replace(',', '')) * 100;
var result = Math.round(num*Math.pow(10,2))/Math.pow(10,2);
document.getElementById('lblWagePercent').innerText = result;
//END
num may have to be converted to a float from a string... if that's the case, use this:
//BEGIN
var num = parseFloat(((igedit_getById('txtNewWage').text.replace(',', '') - igedit_getById('txtCurrentWage').text.replace(',', '')) /
igedit_getById('txtCurrentWage').text.replace(',', '')) * 100);
var result = Math.round(num*Math.pow(10,2))/Math.pow(10,2);
document.getElementById('lblWagePercent').innerText = result;
//END