A Knife, A Penny....

This is a set of nice kitchen knives I received for my birthday (per my request).  As you can see, there is a penny affixed to the package.

When I was young, I was taught of a superstition that when one gives another a sharp object (a knife, scissors, pins, etc), the other party needs to give one a penny in return, otherwise a fight will result.  My mom (sorry Mom) supported this with the example of the fact that my boyfriend at the time and I had just had an argument, and the pins from the corsage he gave me at our recent high school dance resided on our counter.

I've been plagued with randomly handing over pennies at various moments when I needed to borrow scissors in a pinch, etc.  When I received this recent gift, it had a penny attached.  My mom explained that the person in front of her in line was also buying a sharp object as a gift (story in question - again, sorry Mom), and the sales lady suggested this person tape a penny to the package to 'negate the energy'.  So my mom followed in suit.  However, she said she is uncertain this effectively 'works', and casually dropped 'or I can give her 14 pennies, whenever convenient' on several occasions.  (There are 14 knives in this set.)

Has anyone else heard of this superstition?  Is there an 'old wives tale' regarding the exchanging of sharp objects being bad luck.  Does a penny really undo it?  Are there others who abide by this superstition?  Your thoughts?