“…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"
The marketplace probably matters regarding 99 pricing. On Craigslist it looks different than Amazon marketplace or eBay. I sold books on Amazon and all the big sellers used 99 but then when some college kid (with little or no feedback) listed a used textbook they would use a whole number. So, trustworthiness based on 99 doesn’t work that way on Amazon or eBay. The whole number listers are the ones with little sales history and no feedback for you to judge.
I personally use a nickel less than the dollar or $5 less than $100. If I want to sell something for $400 I will list it at $395.