I am currently in Tel Aviv and am constantly struck by the honesty of retailers.
I am reminded of Shakespeare's play about a Jew in The Merchant of Venice. Shakespeare did not know any Jews. They had been driven out of England more than three centuries earlier. He only knew the mythology that remained. That mythology claimed that Jews were cheap, obsessive about money and contracts and crooked. These views were almost the universal view in Christendom.
The cheap part is understandable since Jews were forced by the Roman Catholic Church into the clothing, rags and secondhand business. They had to succeed by keeping costs as low as possible.
The dishonesty part makes no sense based on my experience with the current Israeli population of Jews but also because I've dealt with Jewish immigrants to Israel over the many decades from European countries.
I would like to propose a reason for this false stereotype.
I think it arises from the fact that Jews have been nearly 90% literate and numerate for 3 millennia while the people they lived with during that time were 90% illiterate and innumerate.
I think that kind of difference between a numerate and an innumerate population could result in exaggerating the negative side of every commercial transaction that the innumerates couldn't understand. In simple language, the Christians probably didn't get cheated, they just weren't smart enough to know when they were being treated honestly because they couldn't count.