Ask your manager. A good manager will prefer to answer 10 questions, as opposed to correcting one mistake.
With this kind of keyboard, you can enter whole dollar amounts with the "00" key. E.g., 5, followed by 00 is $5.00.
Other than that, the last two digits you enter are cents. enter 5 4 6 to get $5.46.
Whatever you key in, the display should be correct, with a decimal point. Take your time while you are learning.