Way too many sellers at .33 and .44, .55 doesn't seem to happen.

Selling/Sold at .33:

http://www.tf2outpost.com/trade/12181598

http://www.tf2outpost.com/trade/12121185

http://www.tf2outpost.com/trade/12186031

http://www.tf2outpost.com/trade/12172423

http://www.tf2outpost.com/trade/12177032

http://backpack.tf/classifieds/id/76561198044163148 (1 at .33 atm)

http://www.tf2outpost.com/trade/12170180

http://www.tf2outpost.com/trade/12152836

http://www.tf2outpost.com/trade/12151987

http://www.tf2outpost.com/trade/12190910 (The elusive .22 seller!)

Selling/Sold at .44:

http://www.tf2outpost.com/trade/12188372

http://www.tf2outpost.com/trade/12173945

http://www.tf2outpost.com/trade/12156132

http://www.tf2outpost.com/trade/11442290 Turns down offers of .33, but no offers of .44.

http://www.tf2outpost.com/trade/12192906

Unsolds at .55:

http://www.tf2outpost.com/trade/12047500

http://www.tf2outpost.com/trade/11992462

http://www.tf2outpost.com/trade/12096852

http://www.tf2outpost.com/trade/11987703

http://www.tf2outpost.com/trade/11819819

http://www.tf2outpost.com/trade/12054804

And you get the point.

While there are a decent amount of .33 traders, they get added rather quickly, and it seems possible to sell at .44. That's where the .33-.44 range comes from.