penny-rounding “imposes a tax of $3.27 million Canadian dollars from consumers to grocery stores on a yearly basis in aggregate

https://economics.ubc.ca/news/penny-rounding-profitable-for-...

eliminating the penny would require producing more nickels to “fill the gap in small-value transactions.” But nickels suffer from a similar “seigniorage” problem: the 2024 U.S. Mint report said the five-cent coins have a unit cost of 13.78 cents each.

https://time.com/7215870/trump-us-penny-mint-costs-one-cent-...