TFS,
Asendcharlie has it precisely right, the answer is yes, some jet thrust is apparent, but it is slight. The S-76A has about 100 lbs total at high speed, 50 lbs per engine. Most helos have just a few pounds, below 50.
I was told that the record setting Lynx used all the thrust that the FAI allowed, about 500 pounds, I believe, since they had engine power they could not use due to transmission limits. They necked down the exhausts to increase the thrust and drive the engine temperatures up (at constant output torque).