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 $174.67   11.645%   $195.0103   $195.01   $195.00   $195.00  
  Purchase #2 $132.77   11.599%   $148.17   $148.17   $148.15   $148.20  
  Purchase #3 $245.37   8.466%   $266.143   $266.14   $266.15   $266.10  
  Purchase #4 $26.43   6.122%   $28.048   $28.05   $28.05   $28.00  
  Purchase #5 $53.61   9.635%   $58.7753   $58.78   $58.80   $58.80  
  Purchase #6 $8.86   3.787%   $9.1955   $9.20   $9.20   $9.20  
  Purchase #7 $234.49   11.407%   $261.2383   $261.24   $261.25   $261.20  
  7 purchase totals = $876.20       $966.5804   $966.59   $966.60   $966.50