Walmart here has to ask if they are for a handgun. The register even prompts them to ask.
I wouldn’t tell them anyway. Do they think a criminal is going to answer that truthfully?
The reason they ask about whether ammo is for a handgun or rifle is that you can buy rifle ammo at 18, but you have to be 21 to buy handgun ammo.
A long time ago, I was a clerk in the sporting goods department of a large store. We had to log every ammo sale. That was federal law at the time.