We all know that part of the marketing retailers do is selling almost everything for a price ending in $.99. Psychologically $9.99 looks like less that $10 and $999.99 looks like a lot less than $1,000. It is something that they use to almost trick you into paying more than you planned for something.
Then, you have some major retailers that will usually use the same 99 cent principle, but also use other prices to keep track of their discounts. For example, if you see something in Costco for $4.97, that means that it is on sale, probably down from something like $5.99.
You can check out the chart below for a breakdown of the pricing codes that some major retailers use for setting up their discount prices.
(Image courtesy of Lifehacker)