Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $44.70   7.273%   $47.951   $47.95   $47.95   $48.00  
  Purchase #2 $41.82   8.323%   $45.3007   $45.30   $45.30   $45.30  
  Purchase #3 $71.44   7.761%   $76.9845   $76.98   $77.00   $77.00  
  Purchase #4 $177.75   6.164%   $188.7065   $188.71   $188.70   $188.70  
  Purchase #5 $249.59   8.766%   $271.4691   $271.47   $271.45   $271.50  
  Purchase #6 $22.68   9.652%   $24.8691   $24.87   $24.85   $24.90  
  Purchase #7 $109.28   4.362%   $114.0468   $114.05   $114.05   $114.00  
  7 purchase totals = $717.26       $769.3277   $769.33   $769.30   $769.40