It's not just pennies, it's all coins. In a former life I worked in retail and almost nobody would fish around in their pockets for exact (or even near) change. They'd always hand me bills for their purchase even if they had just completed a transaction and had the coins in their pocket. That was in the 90's, and I still see it happening today, even though I'm no longer in the retail world.
It's not that hard or time consuming if you actually use your change instead of letting it accumulate. I typically have less than a dollar in coins on my person at any given time because I spent it.
If you're paying in cash, you either take time to count the change you're going to spend, or you take time waiting for the cashier to count the change you're going to get. Or you go cashless and avoid the whole thing