This type of protest has been done in the past successfully. Imo it's a great way to protest as it can help get the customers on their side (and spread news) , and it also increases the costs compared to just having the store closed for a day.

I guess it could depend highly on the contract of the employee, as if "taking payment" is not actually stipulated then they wouldn't be breaking their contract - could be possible for someone like a barista who only makes coffee. Admittedly I have no insight into their position types nor contract