Not a lawyer--so don't quote me--but I've worked in retail for years, so maybe some of this random info will give you a place to start your search. Also, the regulations will depend on country and/or state--and the product too, of course.
There are some products that have a manufacturer's suggested retail price listed (most books and automobiles, for instance). Those are set prices, and you can't charge more for them. When I worked at Borders, we used to get a yearly visit from the Department of Weights & Measures just to be sure that we weren't, among other things, charging people higher than the retail price set by the publisher.
But the greater percentage of products don't have set prices. Price fixing is still illegal, but you have to prove that there was an intentional collaborative effort by several businesses to fix the prices. Price gouging is also illegal.
There seem to be more regulations for minimum pricing than for the steeper prices. Just as an example, I think Wisconsin has a law called the Unfair Sales Act, which basically states that retailers may not discount certain items below a certain percentage (or below cost). This is supposed to keep the huge corporations from using loss leaders in their advertising to put the smaller merchants out of business.
Is any of that helpful?