The correct answer should be "while i finish grocery shopping".
This should be correct because it is an adverbial clause that shows at what time the action will happen. "Near the front of the store" might be misguiding because it is not an adverbial clause, it is an adverbial phrase as it does not have a verb to make it a clause.
It's using the same pattern of words in order to show more than 2 ideas that are equal importance to help others comprehend what is being written or being typed
can you show a picture so I can answer