When two equally functioning laptops — one visually attractive, the other less so — were priced at $600, research participants were pretty much evenly split over which to choose; but when the computers were priced at $599, 85% chose the attractive one, says a team led by Jungsil Choi of Cleveland State University in Ohio. The apparent reason is that a price ending in “99” conveys a discount image, which assuages buyers’ anticipated monetary guilt over making a purchase that would feel good as well as be useful.

Source: The odd-ending price justification effect: the influence of price-endings on hedonic and utilitarian consumption