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 $107.53   6.296%   $114.3001   $114.30   $114.30   $114.30  
  Purchase #2 $69.59   9.355%   $76.1001   $76.10   $76.10   $76.10  
  Purchase #3 $92.46   6.659%   $98.6169   $98.62   $98.60   $98.60  
  Purchase #4 $157.65   10.732%   $174.569   $174.57   $174.55   $174.60  
  Purchase #5 $32.89   4.624%   $34.4108   $34.41   $34.40   $34.40  
  Purchase #6 $93.59   13.548%   $106.2696   $106.27   $106.25   $106.30  
  Purchase #7 $164.31   10.815%   $182.0801   $182.08   $182.10   $182.10  
  7 purchase totals = $718.02       $786.3466   $786.35   $786.30   $786.40