The last-ever penny will be minted today in Philadelphia

Many countries eliminated their pennies without chaos or unfair burdens on shopkeepers. In Canada, the process was widely popular after the fact even though newspaper articles prior to the elimination intimated it wouldn't be due to their "both sides" style of reporting.

It's indicative of the current US administration that they managed to screw this up despite many examples world wide of how to do it properly.

Unfair burden?? I think you’re blowing this out of proportion..

Credit card fees are 2-4%. Rounding to the nearest nickel costs at most $0.02 (1,2 round to 0; 3,4 round to 5)

It is cheaper for the merchant to round to the nearest nickel for any transaction of one dollar or more than it is to pay CC merchant fees.

It costs on average 2 cents because without legislative authority to round to closest the retailer must round down and eat up to 4 cents of difference.

Cash costs retailers money too. Safely transporting it to the bank, et cetera. For many, cash is more expensive than credit cards.