This one seems like a pretty easy win. Nickels and dimes are useless - no vending machine takes them, and the cheapest single thing you can buy costs more than a dollar. A child buying one Mars bar at Superstore would spend $1.25 + 11% or $1.39. Rounding that to $1.50 costs that child an extra 8%, if they do not buy anything else. If they bought a pre-made sandwich, it'd cost them $5.00 + 11% or $5.55. Rounding to $5.50 saves them 1% - anything more expensive is a rounding error and an utter waste of time.
It'd be very nice to not have to collect these in a jar, and shove them into the machine that counts them and eats a percentage. It'd be even nicer, to not have grandmas counting the damn things when paying by cash. Yes mom, I'm calling you out - on the internet no less. All the government needs to do is stop purchasing these coins. Then the Royal Mint could shut off the machines. Make an announcement on the CBC, for stores to stop stocking the coins. In good time, the nickel and dime would be gone. :)
The USA is tariffing us and still threatening to annex us, so I'm even more fed up than usual with feet and fractional inches.
Everything else that matters is in metric units already, or both ways. My height is in centimetres on my driver's license. Grocery store scales have grams on them, and bathroom scales have kilograms. My truck is weighed in kilograms at the garbage dump. Semis and trailers are weighed in metric tonnes, unless I'm mistaken. (It's been a decade since I was working highway construction.) Beverages are sold in millilitres or litres, and they are making smaller pop-cans anyways, so the weird sizes don't matter.
The hardware store could stock only metric bolts, nuts, screws, and tools. (But I don't need to wait for them - I'm just going metric in my house. :) Wood screws or self-tapping metal screws are a given. Anything you're building by hand is going to handle the small, less than a millimetre slop, by tightening onto washers. If you're sourcing bolts to replace existing USA bolts, the Bolt Supply House still exists; Your wrenches and sockets are either not made to a millimetre precision, or have worn by about that much anyways. With the space and money saved on USA wrenches and sockets, you can buy replacement metric ones more frequently. ;)