Most receipts are printed on thermal paper, which is not really printed at all — it is heat applied to a coating that continues reacting to heat, light, and time. A receipt in a warm drawer is often unreadable inside two years, which is inside most warranty periods.
What the receipt is actually for
Three things: proving the purchase date for a warranty claim, proving the price for insurance or a return, and reminding you what the machine in the basement actually is. All three are needed at moments when going back to the store is not an option.
Photograph the ones that matter
Not all of them — nobody needs a photographic archive of grocery runs. Anything with a warranty, anything over a couple of hundred dollars, and anything that might be claimed on insurance. Thirty seconds at the counter, filed against the thing it belongs to, and it is still legible in five years when the paper original is a blank strip.