This story has been updated to reflect Dunkin' Donuts' response.
Whole Foods isn't the only store accused of overcharging its customers in New York City.
Residents in New York and New Jersey are suing Dunkin' Donuts for overcharging them, according to The New York Post. The customers say that they were charged sales tax on non-taxable transactions.
The suit says that customers had to pay sale sales tax on ground coffee, coffee beans, and bottled water—all products that are exempt from tax. The transactions occurred near New York City's Penn Station and in Fort Lee, New Jersey.
"Dunkin’ should stop dunking their customers and provide customers with refunds or discounts so they are made whole,” Carl Mayer, the lawyer who filed the suits, told The Post. He estimated that the chain could made made an extra $10 million off New York customers for falsely charging sales tax.
"We are in the process of reaching out to the franchisees identified in the complaint in order to determine whether these taxes were charged to customers," Dunkin' Donuts spokesperson Michelle King said in a statement to Fortune. Dunkin' has more than 1,000 locations in New Jersey and New York, which are operated by individual franchisees.