“That’s called libration and is caused by a couple of factors, but none of them are related to the moon’s rotation.
“That is, the moon is presently in perfect tidal lock with earth, and if it wasn’t for the other factors (orbit inclination, eccentricity, and the observer’s relative position change as the earth rotates), we would always see the same 50% of the moon’s surface.”
Explanation courtesy of Quora’s Fernando Brito, São Paulo State Technological College