So lets say I am watching times and sales for citibank and I see trades whizzing by at bid 4.70 and ask 4.71. I enter an order to buy citi shares at 4.70 .. order sits and sits while I am seeing citi transactions at 4.70 in times and sales, why is my order pending... all of a sudden order executes and guess what... bid is now 4.69 and ask is 4.70 . I have seen this countless times now. any idea why this happens? by the way I am using scottrade.. its not really fancy as it only accepts two decimal places for the share price.