You are NOT required to purchase any extra insurance, it is optional and your choice. Some choose to purchase it and others don't. Your credit card should provide some coverage (if needed). This may also depend on the type of vehicle you rent as to if your credit card provides any coverage. If you are from the states there is very little chance your auto insurance or umbrella policy provides coverage. I think some Canadian members have mentioned having coverage but it would be very rare for a US policy to cover you.

Tax should be in the 9% range or so I believe.