OK OK. Not necessary. (unless you're nitpicky... like me!)
For leveling to the action, I use a set of feeler gauges; stacked up so they barely wedge between the bottom of the scope's turret body (if it's got one) and the rifle's picatinny rail (again, if it's got one). This ensures that the scope and action are truly parallel prior to tightening the rings. Again... nitpicking.