Hello,
Right now, in version 1.3, it's not as straightforward as we'd like it to be.
Probably the fastest solution, assuming that all employees have user logins, is to add rule that allows Sales Representatives to see contact with Login field not empty. It's an imperfect solution with couple flaws, but for most setups that we've seen it should solve your issue without really suffering from any of the flaws.
Another solution would be to create a checkbox field or use/create a group for the Group field that will specifically indicate if given contact can be access by Sales Reps, but the problem here is that requires additional work to set up and maintain it.
In the version 1.3.1, that is just around corner, the Employee clearance is based on explicit value in Access field in contacts, instead of company assigned (Main Company is gone). In that version, you can easily set to allow Sales Reps to view contacts with Access Employee. Until then I'd recommend a temporary solution (no. 1 or using an existing group field value, if possible) since when the new version hits, it'll be very easy to switch it over without additional work.
Kind regards,
Arek