Prepaid taxes and fees

I am buying a phone and looking for a plan. About your $300.00 8 gb prepaid plan, after I pay for the plan, sim and tax (MA sales tax is 6.25). What will the fee's be? Also, will I be paying for the taxes and fees when I purchase the plan, which makes sense to me? I'm trying to find out the total of how much I'll be paying? I am a veteran, but I don't think At&t has a discount for this play.

​

Please help me