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 $173.75   4.841%   $182.1612   $182.16   $182.15   $182.20  
  Purchase #2 $212.58   11.233%   $236.4591   $236.46   $236.45   $236.50  
  Purchase #3 $177.90   8.491%   $193.0055   $193.01   $193.00   $193.00  
  Purchase #4 $46.98   11.395%   $52.3334   $52.33   $52.35   $52.30  
  Purchase #5 $137.92   8.859%   $150.1383   $150.14   $150.15   $150.10  
  Purchase #6 $142.98   12.639%   $161.0512   $161.05   $161.05   $161.10  
  Purchase #7 $58.92   5.334%   $62.0628   $62.06   $62.05   $62.10  
  7 purchase totals = $951.03       $1,037.2115   $1,037.21   $1,037.20   $1,037.30