total tax on a room ressie is 12.5%. 6.5% sales tax and 6% tourist tax I think. So if you are booking a DVC resort with a DVC disount of 25% - 12.5% tax = 12.5% true discount.
For all resort rooms except All Stars and Animal Kingdom the total tax it just about 12.5% For All stars and Animal Kingdom it is just about 13.5% the difference being those resorts are in a different county.