Costco requires a membership, and they do store credit back at higher tiers. They absolutely know what every member buys.
Yes, I'm being charitable but not having to spend part of the refund on an extra program could benefit their customers more in the long run.
(We're Costco members.)
But to save only the "SKU, qty., unit price, date" receipt info - which you would need to process tariff refunds - that'd be maybe 16 bytes per receipt line? To hit even 1TB/day, you'd need a billion customers, each buying 64 items. On that one day.