If the steering wheel is not centered when the car is tracking straight, how do you know the alignment is correct? Are you checking on a level surface?
If you had an alignment done, and the wheel is not centered properly, is not pulling to one side at all, then you should take it back and have them recenter it correctly. If you had an alignment done with a set of old tires, and it behaves this way after new ones were installed, I would get it re-aligned.
However, adjusting the tie rods equally in one direction (lengthen one, shorten the other) you can center the wheel without changing front toe. This may not be the correct alignment, though.
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7