I think so, or at least that's what I've read in 3 of my gardening books....
I have used the pennies, but it's been at least 5 years - all my herbs (except my lemon balm) are all in big containers rather than in the ground, so I use copper tape.
hmmm....that just gave me an idea! I've also got lots of copper tubing I use for crafts...I bet some tubing could be formed into a circle and put at the base of the plant!