Generally, 5 volts is 5 volts. The price shouldn't be a major concern unless   
   you are building a million units. In, ground and out.   
      
   At ½ amp you could probably shunt regulate it, a Zener would only dissipate   
   2.5 watts at no load. Not efficient but probably the cheapest option.    
      
   Between the LM340XX-5 and the 7805, I'd get whichever is cheaper.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)