"This will lower costs for investors as well as improve liquidity, competition and price efficiency in the markets," SEC Chair Gary Gensler said in a statement ahead of the vote. "The one-penny minimum has become outdated. It's too wide in many stocks."

Wall Street's top regulator on Wednesday unanimously voted to allow stock exchanges to price many stocks 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.

The price increments at which thousands of stocks and ETFs are quoted look set for an overhaul Wednesday, when the US Securities and Exchange Commission votes on final rules to reduce them to less than 1 cent.