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 $76.76   7.617%   $82.6068   $82.61   $82.60   $82.60  
  Purchase #2 $12.62   7.749%   $13.5979   $13.60   $13.60   $13.60  
  Purchase #3 $195.90   6.162%   $207.9714   $207.97   $207.95   $208.00  
  Purchase #4 $247.33   5.745%   $261.5391   $261.54   $261.55   $261.50  
  Purchase #5 $223.70   8.497%   $242.7078   $242.71   $242.70   $242.70  
  Purchase #6 $201.42   6.456%   $214.4237   $214.42   $214.40   $214.40  
  Purchase #7 $209.72   4.827%   $219.8432   $219.84   $219.85   $219.80  
  7 purchase totals = $1,167.45       $1,242.6899   $1,242.69   $1,242.65   $1,242.60