need to calculate decimal values

example 42.925181855342466 + 58.64

but i get this $58.64$42.93, i know js is easy on int values, but funny with floats
any help would be great...after some quick helper code...so i can move on.
Code:
Esanda.prototype.calculateFornightCharge = function(payIndex,dueIndex)
	{
		var oThis = this;
		alert("Pay index" +  " " + payIndex + " " + "Due index" + " " + dueIndex);
		var pi = (payIndex-1);
		var di = (dueIndex-1);
		alert("Pay index" +  " " + pi + " " + "Due index" + " " + di);
		var pay = this.oTable.rows[pi].cells[6].innerHTML;
		var due = this.oTable.rows[di].cells[6].innerHTML;
		alert("Due:" + oThis.dollarize(due));
		alert("Due:" + oThis.dollarize(pay));
		var charge = (oThis.dollarize(pay) + oThis.dollarize(due));
		alert( charge );
	}