The MacPOSX Trial [Demo] has a sample database already created so that you can quickly try out the Point-of-Sale interface and its many features.
You can also add your own information to the database. The trial version is only limited to the number of records it will hold, which is 100 and will expire after a period of time.
Any information you enter into the trial can easily be transferred into a purchased registered version. You can remove it by dragging it to the trash.
The download file is in .zip format and you may need to open or double-click to expand it. After expanding you should see the MacPOS Trial v1.5 folder.
Small Monitor support
The trial is setup to be used with 1024x768 screen resolution and using the standard Retail POS layout.