Rounding Numbers

Hello! I am currently working on a… flash thingy in which you click on the stage, and a blue square goes to where you have clicked. Then, a red square pathfinds it’s way to the blue square. The way I choose the blue squares’s _x and _y is as follows (with target_square being the blue square):

onMouseDown = function() {
      _root.target_square._x = _root._xmouse;
      _root.target_square._y = _root._ymouse;

Pretty simple, as you can see. However, I would like to have the blue square’s _x and _y be multiples of 30! Is there a way to do this? Thanks!