I live here in Ontario, and you're right the sky did not fall. The rounding isn't a big deal really, even on scale. It rounds to the nearest nickel, which is or is not in favour of the consumer/business. For example, $2.07 rounds to $2.05, while $2.08 rounds to $2.10. This should net out to an immaterial benefit to either side. It also is only rounded when paying cash. Card transactions are not rounded.

FYI Sales tax is 13% in Ontario now