It's always difficult to talk about etiquette, because, for one thing, the etiquette books do not necessarily represent widespread, common practice: they may give standards that were considered ideal but not always followed, or they may be based specifically on the author's personal beliefs. Conduct manuals were also written for the purpose of helping a middle class audience impress other middle class people and, hopefully, social superiors, particularly if the reader was upwardly mobile and did not grow up with the same type of expectations that they now faced. La science du Monde: politesse, usages, bien-être, published in Paris in 1859 by the Countess de Bassanville, devotes the first section to "la bonne tenue, la toilette, et la propreté", which discusses dress and hygiene; the next, on the duties of the master/mistress of the house, is about holding dinners, receptions, balls, concerts, etc.; the next deals with relationships between family members, events like baptisms, and how to treat one's servants; the next with marriage, weddings, and funerals; the next on writing letters; the next on paying visits and generally dealing with acquaintances outside the home; and the last is on issues relating to the arrangement of one's house. Everything this book explains has to do with presenting yourself to "society" (that is, fashionable and affluent people), enacting social rituals that society will witness, raising children who will feel comfortable in society, and so on. Interacting with shopkeepers in person was not important to this viewpoint.

As a result, the question is really more about character than history. A wealthy man did not have any obligation to bow back to a shopkeeper: you could play it as anywhere on the range from someone cranky who accepts the inequality of the relationship and feels no need to reciprocate, to someone who knows that he is a social superior but is polite and kind enough to give a nod in response. It's up to you as the actor to choose how to play this.