everytime i press a department key(which has a fixed price),then type in the cash amount recieved,then when i press cash/tend(which should bring up the amount of change required) it just beeps and displays EOO.Why is this???

joe, December 2015

You forgot the subtotal button after the department

Registerman, December 2015

You could have done a Google search. I did and found these within 2 minutes:

http://www.justanswer.com/electronics/6517j-hi-er-380-electronic-cash-register-sam4s-haven-t.html#re.v/416/

and

http://howtomendit.com/answers.php?id=501917

Note this second link points you to the manual (though I have not tried that link so cannot confirm it is still valid)

XXX, December 2015