Banks don’t care about “rare” cash. If you’re using conversion kiosks at the airport it’s even less.

https://www.td.com/ca/en/personal-banking/solutions/exchange/currency-converter

You need to report large sums of cash with customs

https://www.cbsa-asfc.gc.ca/travel-voyage/ttd-vdd-eng.html

I would recommend getting them exchanged at a bank for CAD (rather than the airport kiosks), but the banks will exchange any legal tender currency.

Businesses will not accept them directly, you will need to pay Canadian businesses in Canadian dollars.

And yes, as the other commenter mentioned, make sure to declare large quantities at customs. There will be a place on your entry form for large currency amounts.

Banking in Canada is dominated by the Big Five. A branch in a big city should be able to change most currencies into CAD, but they might want you to wait overnight or give notice to change that much money. Not sure about private currency exchanges. Selling RMB, yen or HKD in Vancouver would be easy but you might have trouble selling Kuwaiti Dinars at a small currency exchange in Halifax.

You might be better off exchanging them before travel, you would need to look up rates

A bank probably would, but I don't know if they'd do it for just anyone.

More importantly, if you're crossing a border with large sums of cash, you must declare it at the border.

CBSA is not in the business of stealing money, but they will confiscate it if you don't declare it.

Banks might exchange notes here, but not coins.

CBSA is gonna have questions if you have more than $10000 CAD in cash.

You could try looking at a currency exchange business.

It could be a longshot because of the currency type, but I go to one every now and again to exchange Pound Sterling.