Take a look at using a leather belt with a hidden pocket. It should be large enough for 4-5 bills single stacked and up to 10 double stacked. Or place bills in the hidden pocket or brim of you hat. Place one or two bills under your shoes's footbed.

All kinds of locations to stash cash in the vehicle or at home.

While small bills are fine and necessary don't forget to include a few larger bills like 50s and 100s - literally more "bang for the buck!"