Yea...In US most of the prices tags are like..9.99 and 29.99...I mean most of the people dont care about the extra cent to add to make ot round figure..but still it goes on like this..

I say ...A figure like $99.99 looks lesser than $100.00.. (...my guess..lol) so it appeals buyers that its less than $100 ..hence they are tagged as such..