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 $147.41   9.187%   $160.9526   $160.95   $160.95   $161.00  
  Purchase #2 $226.68   3.521%   $234.6614   $234.66   $234.65   $234.70  
  Purchase #3 $186.31   12.671%   $209.9173   $209.92   $209.90   $209.90  
  Purchase #4 $144.46   5.800%   $152.8387   $152.84   $152.85   $152.80  
  Purchase #5 $199.25   11.725%   $222.6121   $222.61   $222.60   $222.60  
  Purchase #6 $238.59   9.429%   $261.0867   $261.09   $261.10   $261.10  
  Purchase #7 $115.92   5.129%   $121.8655   $121.87   $121.85   $121.90  
  7 purchase totals = $1,258.62       $1,363.9343   $1,363.94   $1,363.90   $1,364.00