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 $196.34   8.311%   $212.6578   $212.66   $212.65   $212.70  
  Purchase #2 $211.34   13.528%   $239.9301   $239.93   $239.95   $239.90  
  Purchase #3 $114.94   8.585%   $124.8076   $124.81   $124.80   $124.80  
  Purchase #4 $104.45   9.580%   $114.4563   $114.46   $114.45   $114.50  
  Purchase #5 $183.28   6.536%   $195.2592   $195.26   $195.25   $195.30  
  Purchase #6 $13.94   4.428%   $14.5573   $14.56   $14.55   $14.60  
  Purchase #7 $58.48   3.164%   $60.3303   $60.33   $60.35   $60.30  
  7 purchase totals = $882.77       $961.9986   $962.01   $962.00   $962.10