You might say "no, not really" right away, since this is a field sales application you want to create and its main purpose is to help employees do their work, not to enjoy the beauty of the design. In this case, Xamarin.Forms will do just fine for you to create a design that won’t flaunt some of the native peculiarities.
But just give it a thought. Even a simple non-native application can have a 100% native look if it is designed on Xamarin.iOS or Xamarin.Android. An application with native navigation and buttons designed just as those on iOS/Android will win the hearts of your employees, allowing them to perform their job in a user-friendly mobile environment. Show your sales representatives some love and they will return it with dozens and hundreds of successfully closed deals.