I think women are more prone to paying exact change than men because of the whole purse phenomenon.
Imagine if you pay cash for most things, and you don't have a coin jar back at home, and you have a purse.
Change gets heavy when added in with all that other junk. It's a PITA to deal with making exact change, but it's even more of a pain to carry around $30 in mixed change in a bag along with other stuff. You don't want to throw away good money, but you don't want to be the stick in the mud holding up the line. No-win situation.
Obvious solution is the home change jar, rolling or Coin-Starring, and a trip to the bank.
But a lot of folks don't like rolling or having large jars of change at home.