gallons are already very binary in their divisions so we don't even have to change those that much. there are 16 cups in a gallon
If you use the usual American speed limits (multiples of 5) and convert to km/hr (the corresponding multiples of 8, close enough) and then express those numbers in octal you get ends-in-zero "round" numbers for all of them! This is my suggestion for highway metrification.