First time I am trying Junit and I am following below link:
http://www.vogella.de/articles/JUnit/article.html
When I run my testClass as Run-As-> Junit Test. It says below thing.
Please help me in figure it out.
Could not launch the JUnit plug-in tests because project 'SalesTax'
is not a plug-in project.
SalesTax: Is the Project Name

I suspect you did create an Eclipse ‘jUnit Plugin Test’ launch configuration which is designed to run Eclipse plugins jUnit tests (in some kind of mocked eclipse environment).
Try to create a simple ‘jUnit’ launch configuration instead.