There are at least two clear benefits of Celie's store for community. The store also provides Celie herself with a point a pride, knowing that she owns property (the store, house, and land).
Your real daddy owned the land and the house and the store. He left it to your mama. When your mama died, it passes on to you and your sister Nettie.
Beyond the good the store brings to Celie, Celie's store offers an opportunity to give Sofia a job. After going through so much, from a broken marriage to prison time to indentured servitude, Sofia has managed to survive and a job at Celie's store finally provides her with a situation commensurate with her skills.
She is able to function as an authority in the space of Celie's store. This role is suited to her and it is one of the things that was taken away from her in many of her negative experiences.
Celie's store also presents a new opportunity for many of the African American residents in the town. They now have an African American to deal with in the store. This shifts the dynamic of the shopping experience in a positive direction, according to Celie.
Interesting question. I would like to answer your question in a simple way. The prime reason that Celie's store change the lives of the women around her in the book The Color Purple because she is in a better mood. She hires people to work around her and makes it a nicer environment.