Ja, vi sier ti komma trettini. -
Ja, we say ten comma thirty nine. (or some says "ti komma ni og tredve" - that is ten comma nine and thirty).
I guess you can keep on using gallon (1 gallon = 4,546 litre, US 3,785 liters) and ounce (1 ounce = 28.3495231 grams) ... and be happy about it ...
In older days we too had these weird measurements like 1 skippund that is as much hay you can carry on you back (around 148 kg), but some says:
(http://www.sizes.com/units/skippund.htm)