If you're shooting using a reference system, such as gap, it's helpful to maintain the same cant, usually almost vertical. People tend to develop a preference for a particular cant over time. I believe it comes as a byproduct of good form, so I wouldn't worry about it too much.
If you're shooting instinctive, you should be able to vary your cant from shot to shot without too much change in the point of impact. Terry has a video available on this site showing him shooting with extreme cants one way and the other.
The important things to learn are good alignment, coming to full draw every time, good back tension, good anchor, and good followthrough.