To round, find the hundredths place, and if the number is under 4, leave it and change the next place to 0. If it's over 4, change the next number to 0 but add 1 to the marked number. Since this number is under 4, we don't change the hundredths, only the thousandths leaving us with 45.830. Since the last number is a 0, you can forget about it and write the number as 45.83.
hope this helps!