Why do Russians put change in a dish?

[Smith, Hunter]

This is, I think, a rather trivial but interesting question.
 
Do any of the Russian anthropologists/sociologists or historians know why in most Russian stores and kiosks, the payment and, subsequently, the change is put on a small plate rather than being exchanged directly from the customer to the merchant's hands (or vice versa in the case of change)?
 
No one I have asked so far has come up with a satisfactory answer. Am I wrong in thinking that this is a uniquely Russian or Slavic practice? I suspect it is and I suspect there is probably some interesting explanation for it.
 
Hunter Smith