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 $59.46   9.549%   $65.1378   $65.14   $65.15   $65.10  
  Purchase #2 $236.83   3.155%   $244.302   $244.30   $244.30   $244.30  
  Purchase #3 $32.31   6.728%   $34.4838   $34.48   $34.50   $34.50  
  Purchase #4 $220.90   3.171%   $227.9047   $227.90   $227.90   $227.90  
  Purchase #5 $201.63   10.418%   $222.6358   $222.64   $222.65   $222.60  
  Purchase #6 $60.91   9.493%   $66.6922   $66.69   $66.70   $66.70  
  Purchase #7 $161.40   7.730%   $173.8762   $173.88   $173.90   $173.90  
  7 purchase totals = $973.44       $1,035.0325   $1,035.03   $1,035.10   $1,035.00