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 $119.77   5.567%   $126.4376   $126.44   $126.45   $126.40  
  Purchase #2 $182.66   6.576%   $194.6717   $194.67   $194.65   $194.70  
  Purchase #3 $166.98   5.639%   $176.396   $176.40   $176.40   $176.40  
  Purchase #4 $133.65   10.538%   $147.734   $147.73   $147.75   $147.70  
  Purchase #5 $165.83   3.753%   $172.0536   $172.05   $172.05   $172.10  
  Purchase #6 $61.49   7.122%   $65.8693   $65.87   $65.85   $65.90  
  Purchase #7 $237.50   12.269%   $266.6389   $266.64   $266.65   $266.60  
  7 purchase totals = $1,067.88       $1,149.8011   $1,149.80   $1,149.80   $1,149.80