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 $103.84   10.461%   $114.7027   $114.70   $114.70   $114.70  
  Purchase #2 $49.56   13.439%   $56.2204   $56.22   $56.20   $56.20  
  Purchase #3 $104.93   3.798%   $108.9152   $108.92   $108.90   $108.90  
  Purchase #4 $32.57   8.673%   $35.3948   $35.39   $35.40   $35.40  
  Purchase #5 $206.79   3.509%   $214.0463   $214.05   $214.05   $214.00  
  Purchase #6 $45.67   3.674%   $47.3479   $47.35   $47.35   $47.30  
  Purchase #7 $69.55   9.739%   $76.3235   $76.32   $76.30   $76.30  
  7 purchase totals = $612.91       $652.9508   $652.95   $652.90   $652.80