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 $182.69   11.714%   $204.0903   $204.09   $204.10   $204.10  
  Purchase #2 $195.71   5.817%   $207.0945   $207.09   $207.10   $207.10  
  Purchase #3 $86.88   12.736%   $97.945   $97.95   $97.95   $97.90  
  Purchase #4 $134.62   13.461%   $152.7412   $152.74   $152.75   $152.70  
  Purchase #5 $117.84   6.711%   $125.7482   $125.75   $125.75   $125.70  
  Purchase #6 $72.63   8.717%   $78.9612   $78.96   $78.95   $79.00  
  Purchase #7 $79.40   5.366%   $83.6606   $83.66   $83.65   $83.70  
  7 purchase totals = $869.77       $950.2410   $950.24   $950.25   $950.20