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 $207.46   13.581%   $235.6351   $235.64   $235.65   $235.60  
  Purchase #2 $53.61   9.396%   $58.6472   $58.65   $58.65   $58.60  
  Purchase #3 $229.26   13.849%   $261.0102   $261.01   $261.00   $261.00  
  Purchase #4 $130.79   13.848%   $148.9018   $148.90   $148.90   $148.90  
  Purchase #5 $85.92   4.789%   $90.0347   $90.03   $90.05   $90.00  
  Purchase #6 $105.71   7.137%   $113.2545   $113.25   $113.25   $113.30  
  Purchase #7 $145.45   6.361%   $154.7021   $154.70   $154.70   $154.70  
  7 purchase totals = $958.20       $1,062.1856   $1,062.18   $1,062.20   $1,062.10