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 $62.55   8.777%   $68.04   $68.04   $68.05   $68.00  
  Purchase #2 $227.54   5.650%   $240.396   $240.40   $240.40   $240.40  
  Purchase #3 $89.46   4.575%   $93.5528   $93.55   $93.55   $93.60  
  Purchase #4 $142.45   12.231%   $159.8731   $159.87   $159.85   $159.90  
  Purchase #5 $60.84   13.250%   $68.9013   $68.90   $68.90   $68.90  
  Purchase #6 $190.62   11.546%   $212.629   $212.63   $212.65   $212.60  
  Purchase #7 $115.63   6.868%   $123.5715   $123.57   $123.55   $123.60  
  7 purchase totals = $889.09       $966.9637   $966.96   $966.95   $967.00