As someone mentioned, I’ve only seen em at Aldi. Some dollar stores keep the carts inside with a pole ro prevent them exiting the store. I’ve mostly lived up and down the east coast (plus some young years in St Vincent and the Grenadines), plus visited a few big cities like Chicago, LA, Vegas. Aside from Aldi, I haven’t seen locked up shopping carts, even at places that have basically a second locked down section of the store for life necessary items like diapers, detergent, etc.

I’m only posting this to answer the question though, as the only thing I care about locked down carts is that I almost never carry quarters (mostly pay card, not cash, and for tolls I have a Peachpass).