Building 3D steps/stairs
 

I am trying to stack some of the 3D boxes from the simple 3D stencils to form stairs for a business presentation, but I cannot get the perspective correct. Everytime I change the size of one of the steps (width, depth or height) I cannot get the perspective to match the step below it. I am particularly stumped because there is no way to rotate the object around the y-axis, only the z-axis.

Any pointers for me?
Thanks!