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 $229.86   6.566%   $244.9526   $244.95   $244.95   $245.00  
  Purchase #2 $245.86   6.384%   $261.5557   $261.56   $261.55   $261.60  
  Purchase #3 $246.69   12.516%   $277.5657   $277.57   $277.55   $277.60  
  Purchase #4 $32.73   6.276%   $34.7841   $34.78   $34.80   $34.80  
  Purchase #5 $196.44   11.321%   $218.679   $218.68   $218.70   $218.70  
  Purchase #6 $17.50   5.149%   $18.4011   $18.40   $18.40   $18.40  
  Purchase #7 $152.27   3.824%   $158.0928   $158.09   $158.10   $158.10  
  7 purchase totals = $1,121.35       $1,214.0310   $1,214.03   $1,214.05   $1,214.20