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 $59.98   3.652%   $62.1705   $62.17   $62.15   $62.20  
  Purchase #2 $78.95   10.434%   $87.1876   $87.19   $87.20   $87.20  
  Purchase #3 $6.68   3.315%   $6.9014   $6.90   $6.90   $6.90  
  Purchase #4 $154.56   5.447%   $162.9789   $162.98   $163.00   $163.00  
  Purchase #5 $183.51   6.748%   $195.8933   $195.89   $195.90   $195.90  
  Purchase #6 $196.86   10.138%   $216.8177   $216.82   $216.80   $216.80  
  Purchase #7 $24.42   11.588%   $27.2498   $27.25   $27.25   $27.20  
  7 purchase totals = $704.96       $759.1992   $759.20   $759.20   $759.20