Not sure about pricing (you can try few pharmacy stores for comparison), but if it's in tablet form, can split in half if got a crease line in middle. else I'd go for 5+5 instead. But after searching for the picture, I'd suggest not splitting as it doesn't seem to have a crease line for splitting. Better 5+5 or just go for 5 and see the effect.

just my 2 cents... me no professional, so you should seek professional advice...