NEW YORK (April 8): Retail brokerage Robinhood Financial did not report a certain type of stock trade it executed for customers last year to a public data feed, according to regulatory data analyzed by Reuters and a source familiar with the matter. So-called fractional shares are offered by many brokerages. They let investors buy a slice of a share instead of the whole thing, so rather than forking out more than $3,000 on a share of Amazon.com Inc, an investor can buy as little as $1 worth.