Students look at albums that sold one million records in one week. They select any artist/album they want and round it, then explain their thinking about HOW and WHY they rounded. I wanted my students to focus on what 10/100/1000/etc. was closest.
Here is an example of what I was looking for: Round to nearest 10....3,378,236 albums is in between 3,378,230 and 3,378,240. It is 4 away from 3,378,240 and 6 away from 3,378,230, that is why I knew to round to 3,378,240.
4.NBT.3 Use place value understanding to round multi-digit whole numbers to any place.