“…the average person treats a price ending in .99 as if it were 15 to 20 cents lower.”
The tendency is called left-digit bias, when the leftmost digit of a number disproportionately influences decision-making. In this case, even though the real difference is only a penny, research shows that, to the average person, $4.99 seems 15 to 20 cents cheaper than $5.00 – which results in selling 3 to 5 percent more units than at a price of $5.00"
Unless you shop at Walmart, which literally promises to not end prices in 0, 5 or 9. All this really means is that most things are $XX.98 instead of $XX.99 tho.
Ending in 98 or 97 or whatever does not negate it. You focused too much on that 99.
“…when the leftmost digit of a number disproportionately influences decision-making”