Rounding whole numbers is a form of estimation that involves finding an answer close to the exact value. When rounding to the nearest ten, numbers ending in 5-9 round up, while numbers ending in 1-4 round down. Similarly, when rounding to the nearest hundred, numbers ending in 00-49 round down and 50-99 round up. Examples are provided to illustrate rounding 83 to the nearest ten (80) and 423 to the nearest hundred (400).