In order to help your kid reinforce Rounding to Estimate, you can let him/her watch the videos attached below;(We watched them in class and kids liked them so much)
Rounding to the nearest ten: https://www.youtube.com/watch?v=CMdck80SHnw
Rounding to the nearest hundred: https://www.youtube.com/watch?v=bx-XKcgKqzc
Enjoy!