Both. Haha. At first it was scattershot and not good. Totally random. But now I essentially have the same flow each time.

Most of the time people aren't too receptive and just say 'uhhh No'. Usually the random cashier making minimum wage does not give a crap and just wants their job to be easy. So my caveat is like... pick your spots. Usually talking to a manager or owner will have more gravitas. Have to sort of read people and the situation. Always ask... but know when it's best to accept the polite answer and then pay with fiat.

Start slow!