I try not to overthink these sort of things -- mostly because I lack the needed skills to do so
For my Wednesday game, starting on Monday or so, I just keep handing $20 bills to everyone that I buy anything for cash with, and at a minimum, by Wednesday, I've got a pocket full of $5's to buy my wife and I into a pair of $10 tournaments (each, total $40 for the night) instead of coughing up two "useless" $20 bills.
If one or two people buy into an event with small bills, the problem starts to go away quickly.
In the tiny cash game on the side, I do the same thing, always buying in only the small bills I have.
tl;dr - bring some change.