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 $148.91   13.862%   $169.5519   $169.55   $169.55   $169.60  
  Purchase #2 $171.59   13.644%   $195.0017   $195.00   $195.00   $195.00  
  Purchase #3 $140.96   6.277%   $149.8081   $149.81   $149.80   $149.80  
  Purchase #4 $24.97   4.727%   $26.1503   $26.15   $26.15   $26.20  
  Purchase #5 $108.59   5.338%   $114.3865   $114.39   $114.40   $114.40  
  Purchase #6 $131.87   8.667%   $143.2992   $143.30   $143.30   $143.30  
  Purchase #7 $156.83   7.848%   $169.138   $169.14   $169.15   $169.10  
  7 purchase totals = $883.72       $967.3357   $967.34   $967.35   $967.40