I would personally check into that before you make such a move. I have not heard of it, althouh I don't currently take EBT, I know a lot of relatives who do, and they all charge tax. You would be loosing money if you don't charge tax on taxable items, because when the accountant does taxes, sometimes they go based off invoices, and in you're case...not good. Check into it, before you try to do that
I think though you may be able to set an EBT sale up as a "customer" and for the EBT customer, F7 then select EBT customer and when this sale is rung up, you can have it set so they don't have to pay any sales tax. Best of luck.