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 $118.86   6.785%   $126.9247   $126.92   $126.90   $126.90  
  Purchase #2 $25.87   4.859%   $27.127   $27.13   $27.15   $27.10  
  Purchase #3 $181.77   9.857%   $199.6871   $199.69   $199.70   $199.70  
  Purchase #4 $193.86   4.237%   $202.0738   $202.07   $202.05   $202.10  
  Purchase #5 $156.41   8.635%   $169.916   $169.92   $169.90   $169.90  
  Purchase #6 $75.87   4.491%   $79.2773   $79.28   $79.30   $79.30  
  Purchase #7 $157.54   3.221%   $162.6144   $162.61   $162.60   $162.60  
  7 purchase totals = $910.18       $967.6203   $967.62   $967.60   $967.60