I am trying to create a perfect cube in Illustrator by creating 3 squares, and rotating them using Effect > 3D > Rotate.
However, the rotate function doesn't seem to work. It creates imperfect rotations and in the end the faces do not match up perfectly.
For instance look at this screenshot (zoom to actual size to see the defect well). The way I did this is create a square using the rectangle tool and holding the shift key, and then rotating it to isometric left. You can clearly see though that it's not rotated perfectly -- the left side especially is not perfectly vertical as it should be.

Is there a way to fix this? Am I doing something wrong?