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 $173.94   13.622%   $197.6341   $197.63   $197.65   $197.60  
  Purchase #2 $172.31   7.189%   $184.6974   $184.70   $184.70   $184.70  
  Purchase #3 $113.25   10.704%   $125.3723   $125.37   $125.35   $125.40  
  Purchase #4 $232.72   5.667%   $245.9082   $245.91   $245.90   $245.90  
  Purchase #5 $184.43   7.716%   $198.6606   $198.66   $198.65   $198.70  
  Purchase #6 $169.84   11.389%   $189.1831   $189.18   $189.20   $189.20  
  Purchase #7 $149.94   10.415%   $165.5563   $165.56   $165.55   $165.60  
  7 purchase totals = $1,196.43       $1,307.0120   $1,307.01   $1,307.00   $1,307.10