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 $249.83   5.228%   $262.8911   $262.89   $262.90   $262.90  
  Purchase #2 $55.88   7.643%   $60.1509   $60.15   $60.15   $60.20  
  Purchase #3 $158.43   12.216%   $177.7838   $177.78   $177.80   $177.80  
  Purchase #4 $241.67   13.193%   $273.5535   $273.55   $273.55   $273.60  
  Purchase #5 $106.59   7.105%   $114.1632   $114.16   $114.15   $114.20  
  Purchase #6 $196.91   13.543%   $223.5775   $223.58   $223.60   $223.60  
  Purchase #7 $48.31   7.142%   $51.7603   $51.76   $51.75   $51.80  
  7 purchase totals = $1,057.62       $1,163.8803   $1,163.87   $1,163.90   $1,164.10