I'm looking for a site to ask questions on business processes like inventory management, point-of-sale, etc. Which Stack Exchange site should I ask?
It depends on what you want to ask. Based on your comment, your question seems to be related with accounting. Unfortunately, there is no Stack Exchange site for accounting.
Accounting: Accounting is a separate discipline, and there is no StackExchange site dedicated to that matter yet.
Or you could try Quantitative Finance (beta) Stack Exchange.
There might be some members who are experts in accounting. I don't see any harm in asking there.