56% of purchases at a self-service gasoline pump in upstate New York ended in .00, well above what would be expected by chance, and an additional 7% ended in .01, likely reflecting failed attempts to stop the pump at whole-dollar amounts, says a team led by Michael Lynn of Cornell. The findings, along with data on tipping and a pay-what-you-want online scheme, show a pronounced consumer preference for round-number payment amounts, the researchers say.
Source: http://www.sciencedirect.com/science/article/pii/S016748701300024X
Consumers Like to Pay in Round Numbers