Yes, you are quite right. I've looked through the code and have not found a place where this was even remotely considered. Further, I don't understand why it WOULDN'T be from a POS stand point. Any and ALL retail stores which deal with food and beverage items in the USA are likely to have a customer base which is subsidized by Food assistance programs. In my area that used to be called Food Stamps, but later was referred to as EBT. (What EBT stands for I have no clue).
It's a program though the USDA and is a large part of the income to retail grocery. Any supermarket that wished to use this system would HAVE to have this support programed into this system.
To further complicate the present coding method, the customers that have EBT type transactions have a balance limit on their card. Any portion of the total transaction which is paid for by their EBT type card MUST NOT be charged sales tax. (The government doesn't like the idea of taxing it's self

This means that if the total before tax was 14.99, and the customer had a balance of 10.99 on their card, this system would have to provide a way to make a payment of 10.99 against the total BEFORE tax is calculated. The sales tax would then need to be calculated on the remaining $4.00 of the purchase.
To accomplish this, the tax calculation would *HAVE* to be done at the final sale and NOT on an item per item basis.
I've considered the changes that would need to be done for this, and so far, I would see a need to modify the ITEMS database to include a check box to flag the item as EBT Approved. (Not all items in the store can be paid with EBT). When the items are added to the transaction, the system needs to add the subtotal for NON EBT items, and a separate subtotal for EBT Approved items. After adding or updating any items in the cart, the tax needs to be calculated on the grand SUBTOTAL. There also needs to be another field in the transaction for that sale for the amount of funds paid by EBT. When this is entered, there needs to be a recalculation of the taxable sale so that the EBT payment processed is deducted from the grand SUBTOTAL and the difference remaining is taxed. To do this, there must be a system wide tax amount (like the one set up in the company information).
That means that there needs to be another field in that database for EBT sales, as well as the sales, and the sales_tax.
I would be willing to contribute some time into the programing of the changes, but would want to have someone to collaborate with so as to not be writing code that someone else is working on, and also not be writing code that BREAKS what someone else is working on.
As for the customers that should be tax exempt, that would require another entry for that customer entry which flags them as tax exempt, and another field for that customers' sales tax permit number. When the tax is calculated it should look first to see if that customer is tax exempt, and if so the tax is entered as "0", and the customer's tax exempt status stated on the invoice or receipt.
Guys, I hope that the authors of this will agree with me that this *IS* an urgent need for this system if it is to be used by markets that sell food to the public. Not all convenience stores process EBT, but the ones that don't want to throw away the money DO.
I could more easily install quickbooks POS and be done with this, but I see SO much potential in this system. I'm willing to invest programing time, or help in a team environment to see this happen.