There is only one rule we need to remember when rounding decimal numbers. If the digit beside the decimal number you will round off is 5 or greater (larger) than 5, you can round up the decimal number by 1.
Let's round off this example to the nearest hundredths.
1.35732
What does the rule say? If the digit beside the hundredths numbers is 5 or greater, round up the number by one hundredth. What is our hundredths number? It's 5. The digit beside 5 is the thousandths number, which is 7.
1.35732
Does the digit beside 5 follow the rule? Yes, it does, so that means we can round up our hundredths number. Our 5 becomes 6, which brings us to our final answer: 1.36.
Now let's round off to the nearest tenth.
45.639
If the digit beside the tenths number is equal to or greater than 5, round up the number by 1 tenth. What is our tenths number in this example? What is the digit beside our tenths number?
45.639
Our tenths number is 6, and 3 is the digit beside 6. We can't round up our tenths digit, so our tenths digit remains and we remove the digit after it. Our final answer is 45.6.
