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   5.425%   $125.8037   $125.80   $125.80   $125.80  
  Purchase #2 $76.66   6.398%   $81.5647   $81.56   $81.55   $81.60  
  Purchase #3 $203.72   6.520%   $217.0025   $217.00   $217.00   $217.00  
  Purchase #4 $149.33   7.464%   $160.476   $160.48   $160.50   $160.50  
  Purchase #5 $92.75   6.582%   $98.8548   $98.85   $98.85   $98.90  
  Purchase #6 $11.34   4.692%   $11.8721   $11.87   $11.85   $11.90  
  Purchase #7 $214.64   6.724%   $229.0724   $229.07   $229.05   $229.10  
  7 purchase totals = $867.77       $924.6462   $924.63   $924.60   $924.80