The case
The anchor store at the end of the mall, where school clothes came from. The founder was James Cash Penney, and the sign has always carried his surname with its extra letters.
"Penny" is a real word and "Penney" is a rare name, so the store gets the real word. It's the same mechanism as Berenstain: a rare spelling loses to a common one.
Why our brains do this
Rare surnames get regularized to the common word they resemble.
Sources: Wikipedia — JCPenney · Wikipedia — False memory: the Mandela effect
