Today I've tried IB's TWS for the first time. I'm papertrading options. And was a bit confused with how options are getting filled with this broker. Let's say we have bid-ask 3.00-3.10. So when I created a limit buy order at price 3.10, I got filled at 3.10. In TOS you almost always get filled at price between bid-ask, so it would be 3.05. When I tried to set 3.05 as a limit price in IB, a window appered saying I can't do it: "Doesn't conform to the minimum price variation for this contract". What does it mean? Am I doing something wrong? Is there any possible way to get filled between bid and ask? Thanks PS When the price was 3.40-3.60 I got filled at...3.60! (in TOS it would be 3.50 guaranteed). I've also tried market order - the same result.