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 $244.53   8.846%   $266.1611   $266.16   $266.15   $266.20  
  Purchase #2 $245.92   9.379%   $268.9848   $268.98   $269.00   $269.00  
  Purchase #3 $208.98   3.315%   $215.9077   $215.91   $215.90   $215.90  
  Purchase #4 $38.96   6.407%   $41.4562   $41.46   $41.45   $41.50  
  Purchase #5 $159.49   9.851%   $175.2014   $175.20   $175.20   $175.20  
  Purchase #6 $247.83   5.391%   $261.1905   $261.19   $261.20   $261.20  
  Purchase #7 $127.68   3.309%   $131.9049   $131.90   $131.90   $131.90  
  7 purchase totals = $1,273.39       $1,360.8066   $1,360.80   $1,360.80   $1,360.90