Yeah, you're going to need something. With tumbled tile your grout space is going to be substantial. You're going to have to cap that off I think.

You don't need a trim piece with that. Just choose the straightest, nicest looking sides for the exposed ends. If you want, you can use regular sandpaper to round over the edge a little more, but I've never found it necessary to do that. Choose your best-looking pieces ahead of time and set them aside so they don't get mistakenly used in the field. Also be on the lookout for the few odd tiles that aren't cut the same size as the others. Usually those pieces are off in one direction only, so the tile isn't exactly square. You can use those for your cut tiles, to minimize waste.