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 $44.48   10.834%   $49.299   $49.30   $49.30   $49.30  
  Purchase #2 $118.26   3.628%   $122.5505   $122.55   $122.55   $122.60  
  Purchase #3 $170.75   4.539%   $178.5003   $178.50   $178.50   $178.50  
  Purchase #4 $183.93   6.280%   $195.4808   $195.48   $195.50   $195.50  
  Purchase #5 $214.63   8.413%   $232.6868   $232.69   $232.70   $232.70  
  Purchase #6 $223.77   11.687%   $249.922   $249.92   $249.90   $249.90  
  Purchase #7 $176.87   5.141%   $185.9629   $185.96   $185.95   $186.00  
  7 purchase totals = $1,132.69       $1,214.4023   $1,214.40   $1,214.40   $1,214.50