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 $86.99   9.289%   $95.0705   $95.07   $95.05   $95.10  
  Purchase #2 $159.74   9.223%   $174.4728   $174.47   $174.45   $174.50  
  Purchase #3 $237.63   10.232%   $261.9443   $261.94   $261.95   $261.90  
  Purchase #4 $144.34   12.619%   $162.5543   $162.55   $162.55   $162.60  
  Purchase #5 $49.47   11.863%   $55.3386   $55.34   $55.35   $55.30  
  Purchase #6 $42.61   9.284%   $46.5659   $46.57   $46.55   $46.60  
  Purchase #7 $195.46   4.611%   $204.4727   $204.47   $204.45   $204.50  
  7 purchase totals = $916.24       $1,000.4191   $1,000.41   $1,000.35   $1,000.50