In 2001, exchanges began listing stock prices in penny increments, as opposed to fractions such as 1/8th or 1/16th of a dollar. The change was intended to simplify pricing and reduce bid-ask spreads. Recently, however, there has been an increasing call to move to higher increments (such as nickel or dime pricing). The rationale is that such a move would promote trading and reduce volatility. It doesn't hurt that it would also allow trading firms to generate more profit. See article here, WSJ.
Dolvin, Steven D., "Changing Tick Sizes?" (2013). All Chapters. 84.