Thanks jollystomper!
When working with our special needs grandson to find employment in the private sector (grocery, drug store, department store), it became clear he would be considered for shelf stocking but not cashier or "check out" positions. And shelf stocking was the lower paying area, or so that was what we observed. Perhaps there are considerations such as his need to work day shift and with supervision available. And a long line of frustrated customers irritated with their wait would not be a good thing for him to deal with as a cashier. So he (we) finally settled for a part time stock shelving position at $13/hr, day shift. It's with a well known, national drug store chain.
I'm having a little trouble navigating the site you included in your post to check on wages in our area vs those in DC, but I'll figure that out later. I'd like to understand if additional training to be able to move to a cashier position would be worthwhile or not. From your links, apparently not.