Although, I still personally believe that coins at least up to the US quarter should probably be abolished. Quarters are really the only thing semi useful as a medium of exchange, and even they are starting to lose their utility. Maybe dollar coins can still be useful.
Yes, this likely means retailers will play games with change, but other times you will come out on top with the rounding. And think about it this way - yes, sometimes retailers played games with the half-penny too. A few decades on, once you've gotten out of the mindset that someone is "cheating you" out of maybe as much as a quarter-penny every transaction, nobody cares, it's not an actual significant amount of money.
there also are significant costs associated with maintaining currency units that small - it costs more than a penny to make a penny, and while sure, that penny gets used through multiple transactions, that also incurs additional costs on everybody who has to handle that penny in every single transaction. The amount of time and energy spent handling that penny probably winds up being dollars over the lifespan of the penny.
this also gives interesting context to the expression "a penny saved is a penny earned" - that expression today would be "a dollar saved is a dollar earned". A penny was actually a decently significant amount of money when that expression was coined, it wasn't literally "every single quarter-penny matters".
The US probably could get by with just $1 and $5 coins.
Metal coins seem like a case of holding onto tradition despite losing the original reason for the tradition.
Plus, quarters are better to flip to make decisions than bills.
They're also much easier to handle when you need many different ones, like when you're trying to assemble an exact amount. I can just look into my wallet and pick out the coins I need, whereas with notes, I'd have to spread them out like an awkward floppy hand of cards and especially if they weren't distinct enough scanning through and finding the right ones sounds plain annoying.
(Plus, 2 dollars is like a quarter 50 years ago....)
The Japanese still love their cash and coins. And even though they have a variety of NFC payment options and credit cards are not as terrible as they once were, their adoption rate is slow.
Do you know any? If I could vet its security and """reasonably total""" privacy, the idea could be tempting - e.g. to buy a cheap device to only do monetary transactions. I am not sure, first of all, how you would transform cash into credit into a personal device.
* Country-specific: prepaid cards like Suica in Japan, purchasable with cash from ATMs.
* Not that cheap: offshore bank account.
* Not legal: crypto card with "borrowed" KYC.
So basically unless you're lucky to be living in a country with a privacy-respecting culture, you have to act like a criminal to regain the basic right to privacy.
Because I also know of systems which are related to banks, but explicitly come from your account, invisibly to the seller - but the bank knows everything.
I have seen anonymous pre-paid cards which had in the back the space for a signature, and were accompanied by instructions such as "must be signed to be valid".