Can a customer leaving Walmart be compelled to produce a receipt to for goods purchased in the store?

Simply, no. Walmart can ask, but the customer can refuse. Walmart is a private entity and can ask. A customer can comply or consent, but the customer can also refuse.

If Law Enforcement came to the scene, they cannot compel a receipt either, unless they have probable cause to believe there is a crime. My opinion is if a customer is leaving the store, what probable cause exists that a crime was committed?

Query: how far does the shopkeeper's privilege permit this type of interaction among retailers and customers?