This is again a problem-solving boomerang is thrown at you but this time they are also looking for "How you deal with sudden technical problems". A good reply would be: Sir, I will immediately DISPLAY a message in front of the WINDOW telling the customer's that the machine is broken, it would be great if you can use another mode of payment. Correspondingly, I will contact the technical team to fix the issue and inform the manager about the situation.

They want to know how experienced you are. Working in different TYPES of retail stores gives great exposure in the industry. If you have worked with big BRANDS, tell them. Explain your daily routine and also tell them about your role in each of the retail stores you worked in. This will help them in judging you whether the working conditions relate to you or not.