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 $56.53   13.117%   $63.945   $63.95   $63.95   $63.90  
  Purchase #2 $84.52   4.296%   $88.151   $88.15   $88.15   $88.20  
  Purchase #3 $129.74   3.773%   $134.6351   $134.64   $134.65   $134.60  
  Purchase #4 $86.52   13.412%   $98.1241   $98.12   $98.10   $98.10  
  Purchase #5 $41.84   10.788%   $46.3537   $46.35   $46.35   $46.40  
  Purchase #6 $204.86   9.533%   $224.3893   $224.39   $224.40   $224.40  
  Purchase #7 $123.81   6.747%   $132.1635   $132.16   $132.15   $132.20  
  7 purchase totals = $727.82       $787.7617   $787.76   $787.75   $787.80