When you around a number what should you do with the digits to the right of the place to which you rounding

If I rounded 213.422 then it would be 213.4. Why? Because if you look at the 2 numbers on the right side of the decimal point, which would be 42, those r the only 2 numbers you have to round.. so if it was 45 or higher then the number would change to 50, if not then it would just round to 40. At the end of the problem you usually get rid of the rest of the numbers including 0.
So basically: If I round 213.(42)2, it equals 213.(40)
If I round 213.(45)2, it equals 213.(50)
-Always remember that the other #'s disappear-