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 $92.67   3.261%   $95.692   $95.69   $95.70   $95.70  
  Purchase #2 $139.54   10.312%   $153.9294   $153.93   $153.95   $153.90  
  Purchase #3 $240.27   10.806%   $266.2336   $266.23   $266.25   $266.20  
  Purchase #4 $9.45   9.246%   $10.3237   $10.32   $10.30   $10.30  
  Purchase #5 $14.34   6.502%   $15.2724   $15.27   $15.25   $15.30  
  Purchase #6 $104.60   9.256%   $114.2818   $114.28   $114.30   $114.30  
  Purchase #7 $93.42   12.763%   $105.3432   $105.34   $105.35   $105.30  
  7 purchase totals = $694.29       $761.0761   $761.06   $761.10   $761.00