A little thought must be put into your tile selection. Many manufactures offer trim pieces that will butt up to the opening. These pieces will have a finished edge. Your tile installer or salesperson should tell you how much to order. Another option which is dependant on your tile material, is to have the exposed edges polished by your installer. Nice trim shows the difference between a beautiful kitchen and a slapped together one. You are going the distance to buy great materials, do it all right!

Most tile selections have a bull nose option used in cases like this where a corner needs wrapped around, or tile needs to end. Bull nose is tile that has one edge rounded and glazed (instead of left raw), so when you install it on the wall the edge looks finished and clean. If you choose a glass tile, or tile that does not offer a bull nose/trim edge, then you can use a Schluter edge trim. Schluter is a piece of metal (or painted PVC) used in cases like this when there is no trim available.

Below are some photos for you to visualize. The first one shows one of my clients backsplashes where we used BULLNOSE to wrap the edges by the window. The second photo is a Schluter edge. This example is of a metal strip, but they also make ones in white/off white/beige/black/etc. Best of luck!