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 $59.96   8.593%   $65.1124   $65.11   $65.10   $65.10  
  Purchase #2 $116.89   5.122%   $122.8771   $122.88   $122.90   $122.90  
  Purchase #3 $170.56   10.591%   $188.624   $188.62   $188.60   $188.60  
  Purchase #4 $91.59   3.840%   $95.1071   $95.11   $95.10   $95.10  
  Purchase #5 $221.49   5.593%   $233.8779   $233.88   $233.90   $233.90  
  Purchase #6 $107.77   7.177%   $115.5047   $115.50   $115.50   $115.50  
  Purchase #7 $104.87   8.638%   $113.9287   $113.93   $113.95   $113.90  
  7 purchase totals = $873.13       $935.0319   $935.03   $935.05   $935.00