ActionScript 3.0 :: Custom TweenLite Function - Stage Pixel Precision

I am doing a custom function like TweenLite.to, but there is one problem. I cast that function on many objects. And they all move a little bit differently. It only happens when I don't do Math.Round(bonus_move). If I use numbers for example 0.58. It moves every stage child differently on about - 0.05.

Here's my function:
Code:
Select allpublic function moveTo(child, speed, px, py){
// configurable
var movement_accuracy = 20;
var delay_duration = 2/(movement_accuracy/10) ;
var movement:Timer = new Timer(speed*12.5*delay_duration, movement_accuracy);
movement.addEventListener(TimerEvent.TIMER, timerListener);
function timerListener (e:TimerEvent):void{
[Code] .....