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 $208.43   13.803%   $237.1996   $237.20   $237.20   $237.20  
  Purchase #2 $55.80   12.267%   $62.645   $62.65   $62.65   $62.60  
  Purchase #3 $18.44   7.295%   $19.7852   $19.79   $19.80   $19.80  
  Purchase #4 $143.63   6.669%   $153.2087   $153.21   $153.20   $153.20  
  Purchase #5 $118.34   3.841%   $122.8854   $122.89   $122.90   $122.90  
  Purchase #6 $173.71   10.669%   $192.2431   $192.24   $192.25   $192.20  
  Purchase #7 $207.72   13.520%   $235.8037   $235.80   $235.80   $235.80  
  7 purchase totals = $926.07       $1,023.7707   $1,023.78   $1,023.80   $1,023.70