I don't know what is preferred, but I always stop the taper exactly at the back edge of the bolster. I keep the taper finish relatively course for epoxy adhesion. I finish the bolster / choil surface of the tang much finer.
I figure that this way, I there is no chance of a visible "seam" at the front of the bolster, as there may be if I continued the taper all the way to the front of the tang.
I hope this makes sense.