Just round to the nearest 5.
30 mph - 50 kph
50 mph - 80 kph
55 mph - 90 kph
60 mph - 95 kph
70 mph (national speed limit) - 110 kph
Pretty much the only speed limits you'll run into. I started the game with a UK truck and upgraded to a Euro one so I learned the conversions pretty quick, even switched the use miles setting in options.
Customizing my DAF, I didn't realize there were all these light bars in the game, non of this is available for the Renault Premium. I used to hate driving at night, no longer an issue with 18 forward facing high beams and room to grow . Didn't notice it was dawn until my I looked in the rear view.