Three mistakes and one commendation in this one... The commendation is for using "he or she" with the antecedent "cashier." Cashier is singular; therefore, he/she is necessary. The second sentence should read "Every customer WHO" because a customer is a person, not a thing. The second mistake is that "every customer" is singular and the pronoun "their" is plural. Since "their" refers to "customer" "their" should be "his or her." The third mistake is that "nest" should be "next." This sign is from a McAlister's Deli in Little Rock.