You can actually get a speeding ticket for even driving just a few miles over the speed limit but it's usually not gonna happen.
When you drive 2 to 10 miles over the speed limit a cop may pull you over if they catch you speeding over the speed limit.
However the cop will likely just give you a warning first and tell you to slow down and not do it again or they'll give you a ticket next time.
That's what happened to me once I was driving 10 miles over the speed limit and really didn't realize it and the cop that pulled me over just gave me a warning to slow down.
Cops will rarely write speeding tickets for going 5 MPH or less over the speed limit but if you're going 15 to 20 MPH or more over the speed limit then you'll almost certainly get a ticket for speeding even if it's your first offense and have to pay around $80.00 to $200.00 or more depending on what your location charges for a speeding ticket.