Extra Charges could be percentage based?

[Rebecca174]

Having a county tax makes it difficult to calculate the charges.  Couldn't it be possible to include an option 'extra cost' as a percentage rather than a dollar amount?

Otherwise, I am trying to calculate the tax we need to report in a backwards way.  Any suggestions from folks who have also dealt with a county or other tax?

[Alice-and-Jeff0]

Multiply the reservation total by the percentage of tax you need to charge.  Then add that number to the the reservation total.  This is your needed amount plus tax.  

EX:  Reservation total = $200 , tax is 6%.  200 x .06 = 12.  $200 + 12 = $212  (total with tax)