If everyone complies, then any retailer can simply sell anonymously. But if some bad apples start to sell smuggled nails from the back of their truck, then the government may start tracking trucks and nail making equipment. That still might not apply to ammo though as long as there are legitimate dealers. I am simply worrying that in their zeal to track everything especially benign things, they will develop the ability to track everything to the purchaser. I can't say specifically how because I don't know how. But I do know that tracking would be necessary to stop the black market.
People such as crafters who make things for resale should simply be considered wholesalers. The people they sell to should be required to collect the tax when the item is sold. If they sell directly to the public, they are a retailer
Fair enough, but just keep in mind some craftsmen I deal use use home made materials that can't be tracked so the new I.R.S. would inevitably suspect them of cheating (selling untaxed or lower taxed units) and send out agents to test their compliance. This could quickly devolve into big government vs the little guy.