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 $62.45   8.821%   $67.9587   $67.96   $67.95   $68.00  
  Purchase #2 $21.63   11.764%   $24.1746   $24.17   $24.15   $24.20  
  Purchase #3 $63.95   7.717%   $68.885   $68.89   $68.90   $68.90  
  Purchase #4 $210.56   13.727%   $239.4636   $239.46   $239.45   $239.50  
  Purchase #5 $165.78   4.650%   $173.4888   $173.49   $173.50   $173.50  
  Purchase #6 $242.76   9.449%   $265.6984   $265.70   $265.70   $265.70  
  Purchase #7 $204.91   11.131%   $227.7185   $227.72   $227.70   $227.70  
  7 purchase totals = $972.04       $1,067.3876   $1,067.39   $1,067.35   $1,067.50