I’m sure other customers were wondering why the crazy lady was taking a photograph of this sign. I had to. I simply had to. If “all” cashiers are not authorized to do the actions listed on the sign, it implies that some cashiers may have that authorization. How is the customer to know who wields that power?
The fact is that “no” cashiers are authorized to make those changes. I guess “all” seemed more inclusive to the sign writer.
See those quotation marks around the information about using credit cards? Nobody said that. Too often, people use quotation marks to call attention to words. Keep them just for quoting spoken or written information from another source.