Rounding

In third grade kiddos are expected to be able to round and estimate numbers.
This is the TEK:  represent a number on a number line as being between two consecutive multiples of 10; 100; 1,000; or 10,000 and use words to describe relative size of numbers in order to round whole numbers


I teach rounding by having kiddos think of number lines as hills.
The middle of the hill separates the numbers that round down and the numbers that round up.
I want them to really understand that we're looking at which number it is closest to.
There are many tricks to teaching rounding but I'd rather them understand the concept first!