Re: self checkout
Half dollar coins are NOT very rare. You can get a roll of them at any bank. They are still legal tender, and still in circulation. They are larger than the new dollar coins, true ... but they are smaller than the traditional "silver dollar" size coin, the last version of which is the Eisenhower Dollar.
Strangely enough, the Eisenhower Dollar is still legal tender, and still in circulation. I see them fairly regularly, a couple times per month (ask for one at your local bank) ... I saw the Susan B. Antony coin fairly regularly when it was first introduced, but not for about two decades now, following the one year re-issue in '99 ... and I have NEVER seen any of the more modern Sacagawea or Presidential dollar coins in circulation. Seems to be little interest in the denomination.