For credit experts only...?

I have good credit, but I have 4 credit cards (retail accounts) that I don't use. I have one credit card through my bank that I do use occasionally. I have no debt. I have heard that closing my unused retail accounts would actually lower my credit score. Is this true? It thought closing them would help my credit, as it seems that people can be denied the best interest rates due to ';a large number of retail accounts.'; Enlighten me please...