I read it as a girl, and I think it may have been passed on by my older cousins, so could be from 1950s.
Set in New York, it was about a family whose children pooled their pocket money and took it in turn to go out for an individual treat. The only one I can remember was one of the daughters wanted her long hair cur off, and whilst it was being done they painted her nails too, which terrified her because of likely parental disapproval. She couldn't get it off and parents spotted it at the dinner table, and minded far less than she'd feared.
The rest of the book had descriptions of the other sibling's treats.
Sorry, it's no much to go on, but does it ring any bells?