No.
They are responsible to pay for the actual tax, or the actual tax they collected, whichever is higher.
They are required to charge the correct tax.
For the seller, Sales taxes are a "trust fund"...that is, it is never his money...he collects the money from the purchaser (who is actually legally responsible to pay it whether he collects or not), on behalf of the State. he hold the money in trust. He cannot guess the amount.