Problem: Our opinion is that it is important to consider about usability in system development. In this thesis we will focus on usability in point-of-sale systems. The point-of-sale system we base this thesis on is Extenda Retail. Our case study is performed on Ica Kvantum in Bromölla, which implemented Extenda Retail about two years ago. Purpose: The purpose of this thesis is to figure out what important factors there are to consider, in usability aspects, when developing point-of-sale systems, with focus on the cashier. We also wish to find out the cashiers opinions about the Extenda Retail system. Method: The information gathered for this thesis consists of literature and interviews. All the information has been studied and analyzed. Result: We have reached the conclusion that the end users consider Extenda Retail to be a good point-of-sale system in usability aspects. It also shows that the guidelines we have chosen, with minor modifications, supports development of point-of-sale systems.