Tagged ammo will be more expensive than the same non-tagged ammo is now.
Demand for pre-tag ammo will go up.
Taxes will be imposed on the ammo to maintain the ammo registry.
No one will want to buy ammo, because it will 'register' their caliber, if not the firearm(s), by providing a database of ammo purchasers.
Of course, the first follow-up laws will ban straw purchases of ammo, or require the reseller to maintain records in perpetuity.
Deformed, distorted or damaged tags may lead to wrongful convictions, there is no guarantee that numerical or alphanumeric tags will not be damaged in handling, firing, impact, or recovery.
Stolen ammo may be tracked back to an innocent person.
Only by maintaining meticulous records of every round or component will anyone have a prayer of 'proving' their innocence.
Tags which are not in plain view (i.e. on the base of the bullet, which would be most likely to survive least deformed) may not correspond with the number on the package, and render the system worse than useless, but lead to wrongful convictions.
My fingers are getting tired, but that should be a good start.
And ammo-running.
But that is the very POINT of the law. To lead to wrongful convictions, to make being a shooter so risky in the legal sense, that in the end more and more of us say "the hell with it" and pack it in.
Once we are a tiny minority, roundly hated by the gunphobic majority, we will be even easier to legislate into extinction.