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 $53.89   6.812%   $57.561   $57.56   $57.55   $57.60  
  Purchase #2 $55.76   13.792%   $63.4504   $63.45   $63.45   $63.50  
  Purchase #3 $65.65   9.594%   $71.9485   $71.95   $71.95   $71.90  
  Purchase #4 $123.82   6.685%   $132.0974   $132.10   $132.10   $132.10  
  Purchase #5 $218.74   9.583%   $239.7019   $239.70   $239.70   $239.70  
  Purchase #6 $245.40   6.676%   $261.7829   $261.78   $261.80   $261.80  
  Purchase #7 $193.96   7.742%   $208.9764   $208.98   $209.00   $209.00  
  7 purchase totals = $957.22       $1,035.5185   $1,035.52   $1,035.55   $1,035.60