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 $206.90   4.844%   $216.9222   $216.92   $216.90   $216.90  
  Purchase #2 $35.42   5.474%   $37.3589   $37.36   $37.35   $37.40  
  Purchase #3 $236.35   13.307%   $267.8011   $267.80   $267.80   $267.80  
  Purchase #4 $181.63   13.653%   $206.4279   $206.43   $206.45   $206.40  
  Purchase #5 $46.40   3.223%   $47.8955   $47.90   $47.90   $47.90  
  Purchase #6 $227.95   3.793%   $236.5961   $236.60   $236.60   $236.60  
  Purchase #7 $114.91   4.368%   $119.9293   $119.93   $119.95   $119.90  
  7 purchase totals = $1,049.56       $1,132.9310   $1,132.94   $1,132.95   $1,132.90