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 $156.61   5.723%   $165.5728   $165.57   $165.55   $165.60  
  Purchase #2 $130.75   13.712%   $148.6784   $148.68   $148.70   $148.70  
  Purchase #3 $244.52   3.757%   $253.7066   $253.71   $253.70   $253.70  
  Purchase #4 $105.95   10.585%   $117.1648   $117.16   $117.15   $117.20  
  Purchase #5 $108.99   6.420%   $115.9872   $115.99   $116.00   $116.00  
  Purchase #6 $178.70   8.216%   $193.382   $193.38   $193.40   $193.40  
  Purchase #7 $201.50   4.597%   $210.763   $210.76   $210.75   $210.80  
  7 purchase totals = $1,127.02       $1,205.2548   $1,205.25   $1,205.25   $1,205.40