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 $193.59   4.296%   $201.9066   $201.91   $201.90   $201.90  
  Purchase #2 $65.31   3.676%   $67.7108   $67.71   $67.70   $67.70  
  Purchase #3 $233.37   4.557%   $244.0047   $244.00   $244.00   $244.00  
  Purchase #4 $15.61   13.595%   $17.7322   $17.73   $17.75   $17.70  
  Purchase #5 $150.41   13.622%   $170.8989   $170.90   $170.90   $170.90  
  Purchase #6 $235.62   10.761%   $260.9751   $260.98   $261.00   $261.00  
  Purchase #7 $118.56   3.274%   $122.4417   $122.44   $122.45   $122.40  
  7 purchase totals = $1,012.47       $1,085.6700   $1,085.67   $1,085.70   $1,085.60