I'd think a $100 bill would be a tough target because few people use those in shopping, and banks are going to scrutinize them very carefully. A $20 would be much easier to disseminate.
I think we will be needing to use more $100 bills -- and maybe put the $500 back into circulation (a great place for President Reagan's portrait, by the by.)
I was just looking at the receipt from a short trip to the grocery store. The total was for $60; only two items listed were under $1.00, and one of those two was an advertised special price according to the receipt. ;-(