Don't know about on-line purchases...probably so.
However, it's quite possible to have boxes of ammo without the TN 10-cent stamp on them. It's supposed to be applied to the
unit sold, so if you bought a case, there should only be a single 10-cent stamp on the case proper...not one on every smaller
subcontainer inside the case itself. WalMart has a bad habit of sticking 4 stamps on a 100-round "case" of shotgun shells...
but I bet you they only pay the 10 cents for the unit sold, and pocket the other 30 cents. But I digress...
Also, I've had the stamps fall off.
I really think you're worrying about nothing.
Just my opinion: that & 10 cents will pay the tax on a box of ammo!
David