Stephen Sprunk writes:
AFAIK, all TVMs in the US and Canada will accept $20 bills. The problem
with doing that is the change you get ...

In Toronto you can buy a single token (for the equivalent of a cash
fare, $2.75) from a vending machine, but you have to pay in coins, so
change is not an issue. (I'm not sure whether they give change from a
$3 or $4 payment -- I never pay single fares and it never occurred to
me to think about it until now. When the present machines were brought
into use, the cash fare was $2, so this was not an issue.)

The machines do take $20 bills, but what you get out is 8 tokens and
$2 in change. Similarly, a $10 bill gives you 4 tokens and $1. The
effective rate of $2.25 is equivalent to the 5 tokens for $11.25 that
you can buy in a store or from a human subway-station fare collector.
--
Mark Brader, Toronto "The walls have hearsay."
-- Fonseca & Carolino