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 $59.67   6.583%   $63.5981   $63.60   $63.60   $63.60  
  Purchase #2 $66.92   10.698%   $74.0791   $74.08   $74.10   $74.10  
  Purchase #3 $52.56   13.653%   $59.736   $59.74   $59.75   $59.70  
  Purchase #4 $161.43   8.778%   $175.6003   $175.60   $175.60   $175.60  
  Purchase #5 $79.60   5.493%   $83.9724   $83.97   $83.95   $84.00  
  Purchase #6 $222.83   6.365%   $237.0131   $237.01   $237.00   $237.00  
  Purchase #7 $74.29   10.328%   $81.9627   $81.96   $81.95   $82.00  
  7 purchase totals = $717.30       $775.9617   $775.96   $775.95   $776.00