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 $182.66   8.591%   $198.3523   $198.35   $198.35   $198.40  
  Purchase #2 $63.56   11.615%   $70.9425   $70.94   $70.95   $70.90  
  Purchase #3 $48.81   3.685%   $50.6086   $50.61   $50.60   $50.60  
  Purchase #4 $243.25   13.260%   $275.505   $275.51   $275.50   $275.50  
  Purchase #5 $73.91   10.456%   $81.638   $81.64   $81.65   $81.60  
  Purchase #6 $192.58   8.281%   $208.5275   $208.53   $208.55   $208.50  
  Purchase #7 $76.65   8.778%   $83.3783   $83.38   $83.40   $83.40  
  7 purchase totals = $881.42       $968.9522   $968.96   $969.00   $968.90