The basic Sales Tax rate in Florida is 6.0% and is on most goods and services. The counties have an option, by vote of their residents, to add a surtax of 0.25%, 0.5%, 1.0% or 1.5% to the state rate.
Orange County, which is most of WDW, has a surtax of 0.5% so purchases (including meals) are taxed at 6.5%.
Osceola County, which has the All-Stars Resorts and Wide World of Sports in it, has a 1.0% surtax so purchases at those locations are subject to a 7.0% tax.
In addition, counties are allowed to have a tax on transient lodging. In both Orange and Osceola Counties it is 6.0%, so all lodging except the All Stars is 12.5% while the All Stars, in Osceola County, is 13.0%.
Here is a working example, using $100.00 as the original bill to make the math show up easily. Note this is for Table Service. At Counter Service there is no gratutity added.
100.00 - Original Amount
*20.00 - Discount
*80.00 - Subtotal
*18.00 - Gratuity Added based on $100
**5.20 - Sales Tax on $80
103.20 - Final amount charged, takes into consideration discount, gratuity and tax.
Without TiW Discount (and still figuring 18% Gratuity)
100.00 - Amount of Bill
*18.00 - Gratuity
**6.50 - Sales Tax on $100
124.50 - Total
$21.30 - Savings using TiW Card.
(Note - At Victoria and Albert's the added gratuity is 20% instead of 18%.)
* Ignore the asterisks; they are there only so the columns/numbers line up properly.