Tiling to Ceiling

We are currently tiling our bathroom and toilet and are planning on tiling up the wall all the way to the ceiling. Problem is, it looks as though the tiles are going to stick out from beneath the cornice by approx. 5-10mm, thereby not making the cornice flush with the top of the tiles. Is there a way around this? We don't want to do a good job and then get to the top of the wall and have it look ordinary because the tiles aren't flush with the lip of the cornice.