You could just butt the molding up to the tile with a return. If the baseboard was thick, say 3/4" ,you could notch out the back and run it to the tub.
Or you could get the bullnose version of the tile and run a tile base molding.
Thanks ron. I hadn't thought of a return. I can try it and see how it looks. I actually bought the tile to do a tile basebord all around but subsequently am second guessing if it will look as good as the wood. Another thing I considered was just to end my tile at the edge of the tub and not go down the side.