Ceiling tile around sprinkler heads

Thanks so much for your advice, unfortunatley i was working in an operating plant and the sprinkler guys installed the heads already, then my phone died so i couldnt check your post, what i did is measure from two sides of the grid and got the center mark, put the tile finish side up and got my chrome cup on there and made sure it was center. Then once it was center i hit it with a hammer and pushed it through making a perfect circle. Then putting it in i raised one end up and put the head through then the other end while raising it at the same time. while a pain in the butt it worked for the time being. thanks for your reply.