How accurate does a torque wrench have to be?

I'm about to start assembling my motor and was wondering about the accuracy of the average click type torque wrench.

Mine isn't that old, and hasn't been used too often. But I was curious about it's accuracy. I measured the length from the ratchet to the handle, and got a bucket of water with a known weight, and calculated that it should take 96 foot pounds to click ( middle to top end of its range) Setting up the bucket on the handle it clicked at about 90-91 foot pounds, so the accuracy seems around 5 percent. Does that number seem right? Now there are some variables that have an impact on the accuracy of my test, but it's still pretty close.

Would this wrench be accurate enough to use to assemble my motor?