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 $230.53   8.712%   $250.6138   $250.61   $250.60   $250.60  
  Purchase #2 $150.43   4.793%   $157.6401   $157.64   $157.65   $157.60  
  Purchase #3 $76.54   9.518%   $83.8251   $83.83   $83.85   $83.80  
  Purchase #4 $227.49   11.688%   $254.079   $254.08   $254.10   $254.10  
  Purchase #5 $207.64   4.739%   $217.4801   $217.48   $217.50   $217.50  
  Purchase #6 $42.39   10.291%   $46.7524   $46.75   $46.75   $46.80  
  Purchase #7 $231.57   8.714%   $251.749   $251.75   $251.75   $251.70  
  7 purchase totals = $1,166.59       $1,262.1395   $1,262.14   $1,262.20   $1,262.10