We need to go the other way -- introduce larger-denomination bills. Assuming there was a good reason to make the highest bill $100 in 1969, calculating for inflation would allow us to have $500 bills. I'd argue for bringing back the $1000 -- and then indexing it to inflation from here on out.

With negative interest rates on their way in, people and organizations are going to start stockpiling big piles of cash. The least we can do is try to make it more cost-efficient.