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 $240.89   8.753%   $261.9751   $261.98   $262.00   $262.00  
  Purchase #2 $115.35   9.839%   $126.6993   $126.70   $126.70   $126.70  
  Purchase #3 $141.46   9.594%   $155.0317   $155.03   $155.05   $155.00  
  Purchase #4 $144.47   6.444%   $153.7796   $153.78   $153.80   $153.80  
  Purchase #5 $125.35   12.668%   $141.2293   $141.23   $141.25   $141.20  
  Purchase #6 $197.67   4.407%   $206.3813   $206.38   $206.40   $206.40  
  Purchase #7 $130.81   12.158%   $146.7139   $146.71   $146.70   $146.70  
  7 purchase totals = $1,096.00       $1,191.8102   $1,191.81   $1,191.90   $1,191.80