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 $146.74   4.716%   $153.6603   $153.66   $153.65   $153.70  
  Purchase #2 $166.31   8.597%   $180.6077   $180.61   $180.60   $180.60  
  Purchase #3 $207.47   7.342%   $222.7024   $222.70   $222.70   $222.70  
  Purchase #4 $235.89   10.707%   $261.1467   $261.15   $261.15   $261.10  
  Purchase #5 $79.43   8.616%   $86.2737   $86.27   $86.25   $86.30  
  Purchase #6 $58.92   7.614%   $63.4062   $63.41   $63.40   $63.40  
  Purchase #7 $173.63   4.109%   $180.7645   $180.76   $180.75   $180.80  
  7 purchase totals = $1,068.39       $1,148.5615   $1,148.56   $1,148.50   $1,148.60