These small .dmp files are actually created by Windows, not RetailPro. Essentially they are very small records that are trapped by your pagefile that records the processes, loaded plugin files and associated applications that are affected during an unexpected termination of an application.
Typically they are saved in the location in which the executable is loaded. Please take a second to read this Windows KB article about the files. Information included about how to identify them and tools you can use to open and read them to assist in determining why they are created.
If using Windows 7 use this link here – http://windows7themes.net/how-to-open-dmp-files-in-windows-7.html
After reading this you should be able to further troubleshoot why these files are created. Keep in mind that the files found in the Retail Pro 9 directory can be tied to any of the executables found in the Retail Pro 9 directory, not just the Rpro9.exe.
The .dmp files can be deleted without affecting Retail Pro function, but will return if some yet to be identified and resolved problem is causing them.
The Windows Debugger mentioned in this article is saved at V:retail pro9_seriesToolsWindows Driver Kit (use WinRar to unzip the ISO file)