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 $119.33   8.624%   $129.621   $129.62   $129.60   $129.60  
  Purchase #2 $42.38   8.743%   $46.0853   $46.09   $46.10   $46.10  
  Purchase #3 $78.26   9.255%   $85.503   $85.50   $85.50   $85.50  
  Purchase #4 $164.35   6.421%   $174.9029   $174.90   $174.90   $174.90  
  Purchase #5 $62.56   13.447%   $70.9724   $70.97   $70.95   $71.00  
  Purchase #6 $236.95   10.182%   $261.0762   $261.08   $261.10   $261.10  
  Purchase #7 $223.27   10.129%   $245.885   $245.89   $245.90   $245.90  
  7 purchase totals = $927.10       $1,014.0458   $1,014.05   $1,014.05   $1,014.10