While there are adjustments on the cruise control module, I don't believe the "increment" is one of them.
There's a centering adjustment - How close to set speed the CC maintains
Low Speed Adjustment - Lowest speed CC will engage
Sensitivity Adjustment - How quickly the servo responds to speed changes.
If I'm falling behind traffic, I just tap twice (or more). Catching up, hold the set until speeds match traffic. Need more, press the pedal/brake. Personally I wouldn't mess with these settings.