Bench rest guys use 5 to get the accuracy scores, but usually 3 shots for sighting in a scope is enough, the rifle should be bore sighted with the eye ball down the barrel looking at the target then the cross hairs of the scope dialed in to that same spot, or laser , optical bore sighter.
Then once you're"on the paper" it's one over one under and guess where the third one is going! If you did your part and there's no wind it's in the bull.