I'll have to defer to the earlier posters as to the tax rate in Texas. However, please note that Federal law prohibits any and all local taxes (including sales taxes) on satellite service; therefore, ONLY statewide taxes can be charged, in ANY state.
Here in Arkansas, satellite service is the ONLY good or service that's taxable at the state level, but exempt at the local level; I pay only 6% state tax on my SBC Dish bill, while the rest of my SBC bill is taxed at 7.5% or higher (except Internet service which is exempt from tax).