Haven't had quite your problem, Harley, but did worry whenever dad went on his long walks , going for his paper, cup of tea at a cafe etc that people might be taking more money than they should off him as he always had to pay with a note once he lost ability to deal with change. In grand scheme of things I think you have to let people with dementia have as much independence for as long as possible, as long as you are reasonably sure they are safe, of course. I would have thought shopkeepers would recognize that your dad was not deliberately stealing so I wouldn't worry too much. Does he carry identification and your contact number? I used to get dad to do this, with a note saying I needed to be contacted urgently if any problems.
Blue sea
Blue sea