Bank currency exchange is not available if you don’t know to plan ahead, and may not be convenient ever

There’s usually a $5 or more minimum, so less than that might as well be trash. Not convenient for tolls

The only option at the border was an ATM, where you can withdraw currency, converted from your bank, but in $20 increments.

Toll booths did not take credit cards or bank cards for an exact payment. This was before electronic tolling but that still might not be a thing at borders