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 $192.80   10.836%   $213.6918   $213.69   $213.70   $213.70  
  Purchase #2 $18.35   5.801%   $19.4145   $19.41   $19.40   $19.40  
  Purchase #3 $157.50   8.631%   $171.0938   $171.09   $171.10   $171.10  
  Purchase #4 $186.46   11.536%   $207.97   $207.97   $207.95   $208.00  
  Purchase #5 $243.60   6.468%   $259.356   $259.36   $259.35   $259.40  
  Purchase #6 $46.88   3.491%   $48.5166   $48.52   $48.50   $48.50  
  Purchase #7 $84.37   11.450%   $94.0304   $94.03   $94.05   $94.00  
  7 purchase totals = $929.96       $1,014.0731   $1,014.07   $1,014.05   $1,014.10