My guess is that both pennies and nickels will eventually go out of circulation. The coins make no sense, because a penny will buy one twentieth of what it used to, and a nickels is worth far far less than a penny used to be worth. One-dollar bills make no sense either, because in inflation adjusted terms they are "really" only worth between a nickel and a dime, depending on your base year.

We should have five and ten dollar coins and eliminate bills of those denominations. And a hundred dollar bill buys less than ten dollars used to, so why should it be thought of as a "big" bill? It is only to make life difficult for drug dealers that we no longer have thousand dollar bills as legal tender.

Yeah, but.... the US govt mint folks have their collective heads up their collective butts if they think they can get people to accept a dollar coin. Just ain't gonna happen. People just don't like carrying around a pocketfull of worthless change, especially coins that no vending machine takes, especially since most vending machines take bills. Paper money is convenient. We seem to have grown beyond the silly notion that metal money has some kind of 'intrinsic' value.

A dollar is not worthless; it is "really" worth between five and ten cents, depending on your base year and index of price level change.

Note that in European countries large denomination coins work just fine. Coins do not have to be large. For example, the old five dollar gold piece was smaller than a penny (which created problems, because in San Francisco it was the exact same size as a bus token, and by mistake people would put them (now worth more than a hundred dollars)into the fare machine. The twenty dollar gold piece was roughly the same size as a half dollar.

Let the dime be the new lowest denomination coin, then a small fifty cent piece (about the same size as a nickel, maybe with a milled edge), and then also a small (thirteen sided?) dollar coin. The five and ten dollar coins would be larger and worth what fifty cent pieces and silver dollars used to be. I hate carrying around wads of one dollar bills.