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 $44.46   9.520%   $48.6926   $48.69   $48.70   $48.70  
  Purchase #2 $234.97   8.403%   $254.7145   $254.71   $254.70   $254.70  
  Purchase #3 $18.75   6.835%   $20.0316   $20.03   $20.05   $20.00  
  Purchase #4 $221.65   3.304%   $228.9733   $228.97   $228.95   $229.00  
  Purchase #5 $214.87   4.347%   $224.2104   $224.21   $224.20   $224.20  
  Purchase #6 $90.53   5.547%   $95.5517   $95.55   $95.55   $95.60  
  Purchase #7 $155.78   4.868%   $163.3634   $163.36   $163.35   $163.40  
  7 purchase totals = $981.01       $1,035.5375   $1,035.52   $1,035.50   $1,035.60