How is my cognition being affected by not taking any memory medication?

At my cashier job at a retail store, it is taking me much longer to count out the money. Sometimes I'm not sure what change I need to give to the customer, yet the amount is on the screen for me to see. I started counting out the change, while looking at the total purchase and not the change that I should be giving back. I do catch myself when I find myself doing this. When I received my change order from the customer service manager, I thought that they gave me the loose unbanded one-dollar bills, but they gave me the banded one-dollar bills. I had just taken the loose bills out of the drawer, so that I could put the banded one-dollar bills under the loose dollar bills. ​