It turns out that it is possible to use supermarket self-checkout machines to buy nothing. The machines also provide receipts as evidence of theses zero-transactions. The soundtrack for this film includes the transcription of one conversation with a staff member who wanted to confiscate the receipt being sung (by Ruby O'Connell-Rogers). The basis for the imagery is the actual receipt obtained during that exchange.
Mocksim: Can I keep that?
Staff: Yes you may.
Staff: There's nothing on it.
Mocksim: I know yea.
Mocksim: It's quite interesting to see a zero.
See also artsproducts.blogspot.co.uk/2016/05/zero-transaction-receipt-poster.html and artsproducts.blogspot.co.uk/2014/12/less.html