#1:
672,591 rounded to the hundred thousand is 700,000, so mark the point at 700,000 value on the line.
672,591 is closer to 700,000 than to 600,000 so it rounds to 700,000.
#2
3,452 = 3,5
180 = 200
$72,481 = $70,000
572,000 = 600,000
950 = 1000
6,495 = 6,000
835,834 = 840,000
96,625 = 96,6
I hope you'll get the idea of rounding with those examples :)