How to finish tiling an outside edge for a shower?
You should NOT treat the top of the curb as a dry area, prepare it the same way as you prepare the shower floor (and it should be sloped toward the shower). I think you should tile the whole top and front of the curb . 

If you cant find a suitable "corner round", you could finish the edge of the tile at the front of the curb, or finish the front edge corner (if you choose to tile the front side of the curb, which I recommend) with grout . 

I do not recommend finishing any tile edge with caulking.