“…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"
I go out of my way to double back and read 4.99 again as 5. I’m sure I’m not immune but I’m doing my best, aye?
I have some respect for the revolutionaries such as Factorio on Steam who refuse to do this. Though at the end of the day that too is, or can (and will) be, just a marketing ploy to stand out.