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 $248.39   8.383%   $269.2125   $269.21   $269.20   $269.20  
  Purchase #2 $85.46   10.796%   $94.6863   $94.69   $94.70   $94.70  
  Purchase #3 $82.31   6.390%   $87.5696   $87.57   $87.55   $87.60  
  Purchase #4 $194.77   10.547%   $215.3124   $215.31   $215.30   $215.30  
  Purchase #5 $68.88   6.496%   $73.3544   $73.35   $73.35   $73.40  
  Purchase #6 $240.75   10.706%   $266.5247   $266.52   $266.50   $266.50  
  Purchase #7 $113.36   6.138%   $120.318   $120.32   $120.30   $120.30  
  7 purchase totals = $1,033.92       $1,126.9779   $1,126.97   $1,126.90   $1,127.00