1) Yes, E-junkie does not handle any actual payment funds; you always receive payment in full (less whatever transaction fee your payment processor deducts).
2) First, view and then download your E-junkie Transaction Log for transctions within the calendar or fiscal year in question:
http://www.e-junkie.com/ej/help.transaction-log.htm
Once you unzip the downloaded file, you will have a tab-delimited text file that you should be able to open or import in a spreadsheet program (e.g., Excel, iWork Numbers, or free software like Gnumeric or LibreOffice/OpenOffice Calc), then just sum up the amounts in the Tax column (if you just select the whole column, your spreadsheet software may show you an instant sum somewhere, like down in the status bar).
