First, students will learn how to round to the nearest 10 or 100 by plotting on a number line.
Watch these Khan Academy videos:
Round to nearest 10 or 100 on the number line by Khan Academy
Next, students will learn how to round to the nearest 10 or 100 using their understanding of place value.
Rounding to nearest 10 and 100 by Khan Academy
Conclude by leading this investigation:
3.NBT.A.1 Use place value understanding to round whole numbers to the nearest 10 or 100.