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 $136.38   4.814%   $142.9453   $142.95   $142.95   $142.90  
  Purchase #2 $81.52   4.821%   $85.4501   $85.45   $85.45   $85.50  
  Purchase #3 $242.48   12.825%   $273.5781   $273.58   $273.60   $273.60  
  Purchase #4 $199.54   7.395%   $214.296   $214.30   $214.30   $214.30  
  Purchase #5 $183.70   3.158%   $189.5012   $189.50   $189.50   $189.50  
  Purchase #6 $24.71   6.167%   $26.2339   $26.23   $26.25   $26.20  
  Purchase #7 $249.81   4.157%   $260.1946   $260.19   $260.20   $260.20  
  7 purchase totals = $1,118.14       $1,192.1992   $1,192.20   $1,192.25   $1,192.20