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 $114.26   8.870%   $124.3949   $124.39   $124.40   $124.40  
  Purchase #2 $118.91   11.159%   $132.1792   $132.18   $132.20   $132.20  
  Purchase #3 $61.96   11.663%   $69.1864   $69.19   $69.20   $69.20  
  Purchase #4 $5.40   12.360%   $6.0674   $6.07   $6.05   $6.10  
  Purchase #5 $199.81   8.252%   $216.2983   $216.30   $216.30   $216.30  
  Purchase #6 $161.88   5.597%   $170.9404   $170.94   $170.95   $170.90  
  Purchase #7 $41.30   12.398%   $46.4204   $46.42   $46.40   $46.40  
  7 purchase totals = $703.52       $765.4870   $765.49   $765.50   $765.50