The customer's purchase includes a bonus towards some game off the DVD juke box, and a worthy cause, both picks off the menu.
The house gets a take off the top, then the worthy cause (e.g. Greenpeace), with the bonus remainder returning to the vendor for potential recycling.
In effect, the vendor is letting the customer invest its charitable donations, thereby giving the customer identity-building ammo, itself an investment in good will (indeed, the customer may designate herself or another customer as a worthy cause, and in some gaming environments -- not just casinos -- this is actively encouraged).
:: FOSS in Vancouver, BC ::