What’s The Deal With Zeros?

I can’t seem to figure out why numbers that end with zero are more significant than numbers that end in, say, 4 or 7 or 9. Why is 30 more significant than 29?

As I sit here staring at the half century mark I can’t help wonder what the big deal is. I’m the same this moment as I was an hour ago, before those numbers clicked up one more. I’m almost certain I have no more wrinkles than I did two day...