This doesn’t fit the sub, bro. :(
I’m a woman who has dealt with immature/misogynistic dudes who think periods are gross and funny and taboo like 3 year olds with poo poo, and I would be really curious to know where this supposedly happened—not because no dude would say this, but because no cashier would say this. They tell you in training not to comment on anything the customer is buying EVER, or you WILL be fired. I doubt anyone, regardless of how dumb they were, would risk their job and future employment prospects to clown someone about her period.
(Side note—a lot of cashiers will make offhanded positive comments on stuff like makeup or candy or seasonal decorations or any fun little stuff a kid is buying, because someone would have to be mildly crazy to be offended by that to the point of filing a complaint to the company. Managers also know and don’t really care about that. However, if someone makes an asshole comment to you like the dude in op’s post, please file a complaint and the person will be removed before you hang up the phone lol)