Many people know the precise rates; it is just that common people do not, which is the whole point. VAT rate is public and I think uniform across the country. Local governments impose various fees and they are not widely known to the public. Relevant accountants and officials know all about the rates but they are not supposed to broadcast it.

I saw a clip of Chinese news broadcast giving shocking rates on Youtube, like a quarter to a third, but unfortunately I cannot find it now. There is little public information about effective sales tax rate. However, people do realize it. High taxes is one reason Chinese tourists buy a lot when overseas; they could see the price difference.