From Scientific American, Why Things Cost $19.95:
if we see a $20 toaster, we might wonder whether it is worth $19 or $18
or $21; we are thinking in round numbers. But if the starting point is
$19.95, the mental measuring stick would look different. We might still
think it is wrongly priced, but in our minds we are thinking about
nickels and dimes instead of dollars, so a fair comeback might be
$19.75 or $19.50.