So my question is regarding spreads that are within a penny, e.g 4.04/4.05. When executing a market order, I'll typically be filled in between the spread (say 4.0423 or 4.055) any idea on how these market makers determine the price I'll be filled at? I've placed multiple orders in succession in the past and have had very different fills such as .xx01 and .xx5 within a second of each other.