That might help trading venues such as the New York Stock Exchange and Nasdaq Inc., among others, to better compete with wholesalers that can quote in finer increments outside of an exchange.

Wall Street's top regulator on Wednesday unanimously voted to allow stock exchanges to price many shares in increments of half a penny, rather than the current minimum size of 1 cent, aiming to promote more competitive pricing and reduce investor costs on the $55 trillion U.