How to finish the edge of my tiles when there isn't a coordinating trim piece?

Most of the tiles nowadays do not have corresponding bullnose or quarter round pieces. It is recommended to leave a straight edge with a bead of grout to finish off the application or use tile profiles such as the ones made by Schluter - https://www.youtube.com/watch?v=Y9CCN9lS5dA.
Learn more about finishing tile edges without bullnose and trim pieces.