Increasingly common at smaller businesses in western Washington (have seen this in Seattle, Bellingham, and occasionally elsewhere).

Even where it's "technically" possible, it's becoming more difficult. Some grocery stores around here don't staff traditional teller lanes at night, shrinking down to only self-checkout, which are card-only machines. To pay cash, you'll have to escalate to the roaming attendant (or at least, I assume they can find some way to accept cash for that transaction? I can't say I've tried)