Programming Samsung ER 5100?

My samsung 5100 is working fine and I have just programmed it usung the manual I want to use this in a bar, call me thick but I cannot figure out how to put a half pint button on to divide lets say fosters by 2 so if a pint of fosters is £2.40 if I hit the half button and then fosters it will come up at a price of £1.20 The same with a dash which is priced at 0.25 for various products ie coke and cordials, finally I would like a miscelaneous button that I could push and ring in my own amount on the numeric keypad and then cash it off.
If anyone knows I would so appreciate this or just tell me where it is in the manual.

Many Thanks

Rod :-)