This efficiency-focused addon buys ammo whenever possible to keep exactly as much ammo as you want in your bag. There is only one command, available by typing either "/aa <number>" or "/autoammo <number>". This is the amount of ammo that the addon will buy up to.
Thanks to everyone who reported bugs and shared ideas, the addon would've still been stuck comparing strings otherwise!
Note: Earlier I wrongfully thought that buying parts of a stack would result in the excess getting "thrown away". That is not the case. Buying just a single item out of a stack of 200 costs 1/200th the price of the stack, rounded upwards to the first copper.
Check out my other addons: