Yeah I agree that's bogus, she could've taken your account # instead of counting on the spot.
I get hundreds upon hundreds of magnetic Canadian dimes in my rolls every year. My CU will take them when I dump. I once made the mistake of exchanging a steel Canadian dime for a silver that a fav teller (BOA) saved from her tray. She became ticked - practically threw that steel dime back at me - I thought she was kidding - not!