How can i fix my ER-180T register?

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