If you find that your left eye keeps trying to dominate and you donl't want to shoot with the left eye closed there is a trick used in shotgunning that might work.

PUt a dab of vaseline onyour shooting glasses where you left eye would look out when your sighting your rifle. This will blur that eye enough that the right will naturally compensate. I have the same problem and use this in my shotgunning, and it does work.