No, not by a long shot. "Here you go" is sloppy and refers only to the delivery of the receipt or the purchase. It says nothing about the customer or, for that matter, the merchant or the employee.
A proper closing thanks, wishes well, and invites back. For example:
"Thank you. Have a great day. Please stop by again." It should be delivered in an upbeat, authentic, and pleasant tone while maintaining eye contact and offering a smile.
Better yet, would be a more personalized version:
"I am glad that you stopped by. Thank you. I hope that your niece enjoys this. Feel free to stop by again. If you can bring her with her; I would enjoy meeting her. She sounds like a great kid. Have a wonderful weekend."