1) Is it better to avoid touching hands at a store while exchanging cash from cashier to customer or vice versa (opposite gender)?
2) if the cashier is handing cash to a customer of the opposite gender, what would be the best way for the customer to respond?
Halachically since there is no hirhur when giving of getting change etc. it is permitted, however it is better to try and avoid actually touching, so it shouldn’t lead to to hirhur. Even though it is preferred to avoid touching however one must use their better judgement and not make a scene or embarrass the cashier.
Rivivos Efrayim 8-596 (1-7).