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 $61.25   10.544%   $67.7082   $67.71   $67.70   $67.70  
  Purchase #2 $97.71   12.390%   $109.8163   $109.82   $109.80   $109.80  
  Purchase #3 $234.89   8.519%   $254.9003   $254.90   $254.90   $254.90  
  Purchase #4 $115.36   8.177%   $124.793   $124.79   $124.80   $124.80  
  Purchase #5 $212.50   12.314%   $238.6673   $238.67   $238.65   $238.70  
  Purchase #6 $108.61   8.299%   $117.6235   $117.62   $117.60   $117.60  
  Purchase #7 $122.94   7.773%   $132.4961   $132.50   $132.50   $132.50  
  7 purchase totals = $953.26       $1,046.0047   $1,046.01   $1,045.95   $1,046.00