No, another register will not be opened so you can get through the like two minutes faster. The manager knows how many registers should be open to satisfy the demand. There will times when you will have to wait longer than others. Deal with the fact you decided to come to the store and checkout the same time many other people. You may have to wait now but ten minutes from now there will be no line and it will be a waste to open a new register. If a new register were to open it would do ten transactions and then no longer be needed. All the third register will do is create more work for the store to close at night because the drawer will need to be counter down and more paper work will need to be filled out.