They don't exist in circulation. Meaning from my standpoint, at no transaction point will a cashier give me a penny or five pennies back because they don't exist for all intents and purposes.
I wish I would have kept the 1 and 2 dollar bills but even then. they are still in high abundance for the forseeable future, the supply will always probably be high to some degree for the next 100 years or more since people all thought the same at the time, "let me change this $500 into 500 $1 bills and one day I will be rich!" I have a few pennies that were just lying around. In time, they will of course be worth more but nothing compared to the bills that were discontinued.
Meh, I remember Gretzkys rookie card was going for $900 mint when I was in university. I can't tell you how much more that card is worth today. I still have a second year card of his, meh.