How do you know?
Well, 20+ years in retail starting as high school help working up to Store Manager and dealing with/repairing the inner and outer workings of old NCR mechanical registers, digital registers using thermal tape printed receipts, fax machines, etc. will get you to the point where you know by the look.
CVS, Home Depot, etc. use the same technology for their receipts.
I will never work retail again. To paraphrase Patton, I'd shovel shit in Louisiana before doing that type of work again.