How can I rotate in steps with After Effects?
Figured out how to do it with expressions. You need to know the time taken for a full rotation and the number of degrees you want to increment.

degrees = 6; // Number of degrees to rotate by
fullRotationTime = 60000; // Number of milliseconds to complete a full 360 degree rotation

steps = 360/degrees; // Number of steps in one rotation  
divisor = fullRotationTime / steps; 

ms = 1000*time; // Milliseconds since start
degrees*(Math.floor(((ms)/divisor)%steps))


This example will "tick" once a second for 60 seconds.