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 $114.95   10.726%   $127.2795   $127.28   $127.30   $127.30  
  Purchase #2 $153.88   12.808%   $173.589   $173.59   $173.60   $173.60  
  Purchase #3 $246.54   5.844%   $260.9478   $260.95   $260.95   $260.90  
  Purchase #4 $42.65   3.382%   $44.0924   $44.09   $44.10   $44.10  
  Purchase #5 $186.79   12.142%   $209.47   $209.47   $209.45   $209.50  
  Purchase #6 $246.36   9.275%   $269.2099   $269.21   $269.20   $269.20  
  Purchase #7 $165.28   9.682%   $181.2824   $181.28   $181.30   $181.30  
  7 purchase totals = $1,156.45       $1,265.8710   $1,265.87   $1,265.90   $1,265.90