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 $214.65   10.217%   $236.5808   $236.58   $236.60   $236.60  
  Purchase #2 $248.58   5.276%   $261.6951   $261.70   $261.70   $261.70  
  Purchase #3 $76.37   9.675%   $83.7588   $83.76   $83.75   $83.80  
  Purchase #4 $134.74   5.508%   $142.1615   $142.16   $142.15   $142.20  
  Purchase #5 $169.85   3.455%   $175.7183   $175.72   $175.70   $175.70  
  Purchase #6 $152.26   9.797%   $167.1769   $167.18   $167.20   $167.20  
  Purchase #7 $70.49   5.872%   $74.6292   $74.63   $74.65   $74.60  
  7 purchase totals = $1,066.94       $1,141.7206   $1,141.73   $1,141.75   $1,141.80