Randal Olson made this chart using Federal Reserve data showing that over the past twenty years the $100 bill has come to comprise a large and growing share of the total amount of US currency notes in circulation even as the amount of physical cash around rises steadily:

And of course since a $100 bill is worth more money than a smaller bill, the total value of currency in circulation turns out to be all about the Benjamins:

What you're seeing here, basically, is that as cash is increasingly marginalized by cards and electronic payments for everyday transactions the practical role of paper money is more and more shifting away from everyday purchases. Most Americans rarely if ever handle $100 bills. But they're extremely convenient if you're trying to do illegal transactions, trying to save money in a foreign country with a dodgy banking system, or just for your basic tax avoidance.

And even though the $20s and smaller that are the stuff of everyday life are still a large majority of the total bills in circulation, the vast majority of the monetary value of paper currency is locked up in those $100s.