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 $117.82   7.559%   $126.726   $126.73   $126.75   $126.70  
  Purchase #2 $61.81   10.485%   $68.2908   $68.29   $68.30   $68.30  
  Purchase #3 $23.40   4.511%   $24.4556   $24.46   $24.45   $24.50  
  Purchase #4 $116.87   12.173%   $131.0966   $131.10   $131.10   $131.10  
  Purchase #5 $73.61   3.527%   $76.2062   $76.21   $76.20   $76.20  
  Purchase #6 $235.66   11.242%   $262.1529   $262.15   $262.15   $262.20  
  Purchase #7 $206.33   13.187%   $233.5387   $233.54   $233.55   $233.50  
  7 purchase totals = $835.50       $922.4668   $922.48   $922.50   $922.50