1. Go to Your Shop > Options > Download Data > Orders (csv type). Be sure to leave the month unselected and just choose the year if you want your yearly total.
2. Once you download the file for 2012, open in Excel and find the column named "Card Processing Fees" (column W).
3. Use the sum function to total up the column and you should have your yearly DC fee total! The formula in Excel is =SUM(W2:W***). *** should be the very last row number at the end of your spreadsheet, which will vary for everyone depending on how many sales you had.
P.S. If you do not have Microsoft Excel available to you, OpenOffice and GoogleDocs are great alternatives for viewing CSV and XLS files!