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 $116.80   7.708%   $125.8029   $125.80   $125.80   $125.80  
  Purchase #2 $137.72   12.335%   $154.7078   $154.71   $154.70   $154.70  
  Purchase #3 $235.96   9.123%   $257.4866   $257.49   $257.50   $257.50  
  Purchase #4 $113.85   7.498%   $122.3865   $122.39   $122.40   $122.40  
  Purchase #5 $250.65   4.369%   $261.6009   $261.60   $261.60   $261.60  
  Purchase #6 $50.66   5.187%   $53.2877   $53.29   $53.30   $53.30  
  Purchase #7 $169.74   13.371%   $192.4359   $192.44   $192.45   $192.40  
  7 purchase totals = $1,075.38       $1,167.7083   $1,167.72   $1,167.75   $1,167.70