Our loadsheet is provided to the nearest kg. There is no facility to put decimals in for weight.
We tend to round up to the neares 100kg eg a zero fuel weight of 26343kg would be entered as 26400kg.
On the issue of fuel, the FMS speaks to the fuel gauges. It is possible to enter a fuel figure manually, but it is done rarely - normally you would only do it if you enter the ZFW before the a/c has been refuelled.
Fuel gauges read to the nearest 10kg on the a/c I fly.
Decimal points are used for stabilser trim settings and flight path angles and not much else.
There is a page on our FMS that allows us to work out that a 10663ft runway is 3250m long and do other conversions, but we do not mix units.
A weight is kg, fuel qty is kg, altitude is ft, speed is kts, pressure is mbar (or psi for hydraulics)