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 $177.58   13.696%   $201.9014   $201.90   $201.90   $201.90  
  Purchase #2 $240.85   8.590%   $261.539   $261.54   $261.55   $261.50  
  Purchase #3 $54.98   7.690%   $59.208   $59.21   $59.20   $59.20  
  Purchase #4 $208.82   10.489%   $230.7231   $230.72   $230.70   $230.70  
  Purchase #5 $69.42   5.732%   $73.3992   $73.40   $73.40   $73.40  
  Purchase #6 $92.81   5.200%   $97.6361   $97.64   $97.65   $97.60  
  Purchase #7 $10.68   8.671%   $11.6061   $11.61   $11.60   $11.60  
  7 purchase totals = $855.14       $936.0129   $936.02   $936.00   $935.90