I only taper them slightly. Chuck up a nail in the drill press and file it down a bit. When I drill a hole, no matter how I do it, the hole will NOT be the same diameter from one end to the other. The "upper" end gets "wallered" out just a bit. SO, I go with it. I generally drill my barrel/rod pipe/triggerguard tenons with a #43 drill bit (which I think is .089"). I have some nails that are about .095" and I file the end down to fit. I make sure that the pin fits the hole in the metal part before banging the thing together...which could prove problematic! Once the gun is finally finished, the pins should virtually NEVER need to be taken back out again, though while I am working on the gun, I know I take every part apart and put it back together a thousand times.
I have one old German gun where the pins are all tapered, and rather dramatically too. I have another, but I don't remember if the trigger and triggerguard pins are tapered or not, and the buttplate tang pin I simply CANNOT get out...probably because it's straight!!! I have a New England rifle too, but none of the barrel tenon pins are likely to be original (in fact, one is still missing). The rod pipe pins are filed flush with the wood (like you see on SO many old guns). They used "working" pins, or simply left them long while working on the gun, and when finished, they put the pins in, cut them off, and filed them flush with the surface of the wood. I'm scared to try to drive any of the rod pipe pins out, since the ends are not flat. They look rather straightish though.