Ethies, I used to carry a Spyderco Endura with full serrations in college (Class of 1993, Cornell College, Mt Vernon) and never had a beef with anyone, including a cop searching my car with "probable cause." The cop did swipe my $7 walmart special in the glove box which looked and felt like a piece of junk.....
As far as $100 goes, that's a pretty good bridge - is the law five inches of edge or five inches of blade?
I think you would do well with an Entrek Cobra or Companion, neither one can be looked at as a weapon/ dagger, either one will do fine as a tool as well.
Both are built of 440C steel, have a good and useable handle, are fairly bulletproof in their construction, and can be had online for about $100. (Okay, $109 and $114)
Try
www.knifecenter.com and look under Entrek knives - not flashy, no newfound wunderstiels, just good solid knives in a very useable package. I have used a Companion for everything from landscaping to discreet carry with no issues any way around.
You may also want to look at the Entrek Survivor, it is a five-inch bladed Tanto, in the event you like Tanto blades. I don't recommend the tanto point but the knife is durable as hell.
Again, I have carried and used the Companion and did so under various conditions and in all sorts of weather for over a year and I loved the knife - it was one of those stupid decisions to sell it a while back.
If you can find one, a Spyderco Perrin is also a fine carry with your intentions in mind, as are the Spyderco Moran blades - either the upswept or drop-point blades.
Parker