round numbers with units

hello,

im trying to get best wey to round numbers with units like 5.123456789 V

im using the function round(x)

but shows error for units not compatible

need to use the rounded value to show on summary results

right now im using this functions to round and display the results

 but this basically remove the units and convert my variable over and over to number and string, to be able to display it as result.

as you can see below

but i want to show that result is actually 3.33 V 

I also have calculations for current, and capacitance, so I need function to keep different used units.