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 $102.91   11.443%   $114.686   $114.69   $114.70   $114.70  
  Purchase #2 $111.83   10.870%   $123.9859   $123.99   $124.00   $124.00  
  Purchase #3 $99.91   9.789%   $109.6902   $109.69   $109.70   $109.70  
  Purchase #4 $9.97   6.280%   $10.5961   $10.60   $10.60   $10.60  
  Purchase #5 $63.55   7.199%   $68.125   $68.13   $68.15   $68.10  
  Purchase #6 $241.42   5.831%   $255.4972   $255.50   $255.50   $255.50  
  Purchase #7 $164.25   12.856%   $185.366   $185.37   $185.35   $185.40  
  7 purchase totals = $793.84       $867.9464   $867.97   $868.00   $868.00