It's not a surprising finding if you've ever been in sales, it's purely a mind trick- it's the same reason that everything is *.99 not just $x, evenly. Consumers as a whole perceive the $x.99 to "feel" cheaper than that one cent to round it to $x. The normal explanation for this is that people scan the number and whatever the "dollar" amount is determines it's value, so obviously $9.99 feels "cheaper" than $10 because you see the $9 first. Sound ridiculous? I agree, but we (consumers) do actually think that way, if only subconsciously.
