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 $207.48   9.145%   $226.454   $226.45   $226.45   $226.50  
  Purchase #2 $233.36   8.769%   $253.8233   $253.82   $253.80   $253.80  
  Purchase #3 $175.87   11.176%   $195.5252   $195.53   $195.55   $195.50  
  Purchase #4 $15.87   8.499%   $17.2188   $17.22   $17.20   $17.20  
  Purchase #5 $31.36   12.128%   $35.1633   $35.16   $35.15   $35.20  
  Purchase #6 $236.97   10.531%   $261.9253   $261.93   $261.95   $261.90  
  Purchase #7 $58.92   6.372%   $62.6744   $62.67   $62.65   $62.70  
  7 purchase totals = $959.83       $1,052.7843   $1,052.78   $1,052.75   $1,052.80