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 $217.95   7.232%   $233.7121   $233.71   $233.70   $233.70  
  Purchase #2 $65.96   11.505%   $73.5487   $73.55   $73.55   $73.50  
  Purchase #3 $67.90   6.720%   $72.4629   $72.46   $72.45   $72.50  
  Purchase #4 $190.63   12.481%   $214.4225   $214.42   $214.40   $214.40  
  Purchase #5 $9.71   9.557%   $10.638   $10.64   $10.65   $10.60  
  Purchase #6 $239.58   3.163%   $247.1579   $247.16   $247.15   $247.20  
  Purchase #7 $22.50   8.511%   $24.415   $24.42   $24.40   $24.40  
  7 purchase totals = $814.23       $876.3571   $876.36   $876.30   $876.30