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 $114.68   6.439%   $122.0642   $122.06   $122.05   $122.10  
  Purchase #2 $127.29   4.204%   $132.6413   $132.64   $132.65   $132.60  
  Purchase #3 $116.70   8.116%   $126.1714   $126.17   $126.15   $126.20  
  Purchase #4 $240.98   3.243%   $248.795   $248.80   $248.80   $248.80  
  Purchase #5 $154.76   9.458%   $169.3972   $169.40   $169.40   $169.40  
  Purchase #6 $49.72   8.348%   $53.8706   $53.87   $53.85   $53.90  
  Purchase #7 $190.84   13.395%   $216.403   $216.40   $216.40   $216.40  
  7 purchase totals = $994.97       $1,069.3427   $1,069.34   $1,069.30   $1,069.40