A lot of money laundering involves traceable transactions, no? The point isn't to hide the transaction but rather have a plausible explanation for it that's difficult or impossible to verify. I'd think a larger issue would be that you can't plausibly charge very much per swipe. I'm betting there's much easier ways to launder cash these days with so many digital goods and services with basically arbitrary profit margins than brick-and-mortar storefronts can provide.

Granted, there are benefits to laundering money with literal cash, but you still want some legitimate money trail even if you don't actually hand over the claimed goods or services—enough at least to cover the actual expenses of the business, i'd presume.