Also ask for ones if you want to find star notes. I have found about 10 of them in my limited CRH activity only one of them is in great condition but I still keep them all because they're fun to find.
I would say one and fives b/c the ones you might come across a "barr" note or some silver certificates which are hard to find in circulation and the fives you may find several red seals or blue seals. just a thought