This isn't really a QlikView question as potentially the business can position this in either category depending on thier business model. I would recommend you get clarification from you business.
I have done some work with Travel Agencies. Retail often covered several sources of revenue such as holiday sales, property letting, currency exchange. Sales was usually specific to their primary revenue - holiday sales. But it does depend on how the Travel Agency is set up as a company. Both Retail and Sales are valid options.
This tends to be put under its own business sector of Travel and Leisure that covers everything from Travel Agencies through Hotels, Airlines and Funparks, etc.
