The cashier should be entering a tare before weighing and charging. When they scan the item or enter from a scan sheet it's probably already calculated.
How could you get the tare weight with the beans already in the bag, at the register? Cannot be done.
So it would have to be pre-calculated for the proper weight at scanning.
I do not know what kind of bags Whole Foods supplies.
Out of curiosity I weighed my bags(empty)
1lb. kraft/poly lined---.6 oz.
12 oz. kraft/poly lined---.4 oz.
12 oz. & 1lb. foil/poly ----.6 oz. No labels(surprisingly weighed the same!)
2 lb. foil/poly----.8oz.
So, overall you would be losing at most an ounce, generally even with labels under an ounce.
Sometimes I weigh the beans on the scale(bag already tared), then add 12oz. or 1lb. etc. Sometimes I weigh the exact measurement of the coffee
and then pour into bags. As I stated above, if I sell 12 oz. or any advertised weight, you will receive just that.