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 $64.45   13.790%   $73.3377   $73.34   $73.35   $73.30  
  Purchase #2 $237.78   12.646%   $267.8497   $267.85   $267.85   $267.80  
  Purchase #3 $58.49   10.195%   $64.4531   $64.45   $64.45   $64.50  
  Purchase #4 $199.68   12.218%   $224.0769   $224.08   $224.10   $224.10  
  Purchase #5 $38.69   7.341%   $41.5302   $41.53   $41.55   $41.50  
  Purchase #6 $186.73   3.132%   $192.5784   $192.58   $192.60   $192.60  
  Purchase #7 $222.45   7.510%   $239.156   $239.16   $239.15   $239.20  
  7 purchase totals = $1,008.27       $1,102.9820   $1,102.99   $1,103.05   $1,103.00