Good point. I'm sure studies have been done and merchants set such prices accordingly.
This guys appears to have reviewed a number of studies and concurs. BUT...he also thinks that "round" pricing may support luxury branding better. That's partly why you probably can't do simple pricing difference between the same product at the same store.
http://www.sciencedaily.com/releases/2011/09/110906144036.ht...
More about the topic: http://www.quora.com/Pricing/Do-prices-at-99-instead-of-1-00...
Better data would be the same product sold in .99 and .00 versions. I imagine the conversion rate differences wouldn't be so dramatic in that chart.