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 $241.27   8.205%   $261.0662   $261.07   $261.05   $261.10  
  Purchase #2 $127.61   7.125%   $136.7022   $136.70   $136.70   $136.70  
  Purchase #3 $174.28   6.119%   $184.9442   $184.94   $184.95   $184.90  
  Purchase #4 $176.80   9.272%   $193.1929   $193.19   $193.20   $193.20  
  Purchase #5 $21.89   12.277%   $24.5774   $24.58   $24.60   $24.60  
  Purchase #6 $216.90   11.576%   $242.0083   $242.01   $242.00   $242.00  
  Purchase #7 $122.71   13.699%   $139.52   $139.52   $139.50   $139.50  
  7 purchase totals = $1,081.46       $1,182.0112   $1,182.01   $1,182.00   $1,182.00