As you might have guessed with the prevalence of credit and debit cards, the demand for bills have also been going down as reported by this New York Times article
Production of $5 bills also dropped to the lowest level in 30 years. And for the first time in that period, the Treasury Department did not print any $10 bills.
However, the $100 bill is growing in popularity. But it's not due to inflation:
Last year Treasury printed more $100 bills than dollar bills for the first time. There are now more than seven billion pictures of Benjamin Franklin in circulation — and the Federal Reserve’s best guess is that two-thirds are held by foreigners