The industry standard is 3 shots, even GA Precision's accuracy guarantee is 3 shots.
3 is easy and 5 is what I shoot mostly when I shoot groups. Though I have gotten off the bench for most of my shooting and have been shooting steel.
This is a fun excersize nothing more, I never did get my best accuracy off a bipod even with 5 shots. 10 shots tell you what the rifle is doing but also what you are doing. If I was looking for the best groups, I would use a front bag and let the barrel cool between shots or at least groups. but the range was closed this evening for the monthly meeting, maybe I can find a dry day to get out soon.