Can I stop my junior staff from seeing the cost price and my profit on each booking?

Yes, in most cases you can. Travel agency software is normally set up so that every member of staff has their own login, and each login is given a role that decides what that person can see and do. A role meant for counter staff or junior consultants can be allowed to search, book and print documents while the cost from the supplier and your markup stay hidden, so they only ever work with the selling price the customer pays.

The same idea usually applies to reports. You can often limit a junior login to its own bookings rather than the whole office, and keep the sales and margin reports for yourself and your manager. Settings like markup rules, supplier connections and agent credit limits are normally kept in an owner or admin role as well, so nobody can quietly change how your pricing works.

How far this goes depends on your plan and on how the portal is set up for you, so it is worth being specific about which screens you want locked down rather than assuming everything is covered. There are also leaks that no permission setting can close. If a supplier sends a confirmation email or a voucher that shows the net rate, or if your staff have their own logins to a hotel extranet, they will see the cost that way. Emails forwarded from your inbox can do the same.

The practical next step is to write down the screens and reports that matter to you, ask for a test login with the junior role, and click through it yourself before you hand it to your team.