Discovery Education
Discovery Education: Web Math: How to Round a Number
This site provides a description and helpful hints on how to round numbers to any place value. Content also includes an interactive problem solver complete with a full description of how the answer was accomplished.
Khan Academy
Khan Academy: Round to Nearest 10 or 100
Practice rounding to the nearest ten and rounding to the nearest hundred. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video tutorial, or receive hints about rounding.