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	$200.32	3.243%	$206.8164	$206.82	$206.80	$206.80
Purchase #2	$233.85	3.832%	$242.8111	$242.81	$242.80	$242.80
Purchase #3	$190.70	7.712%	$205.4068	$205.41	$205.40	$205.40
Purchase #4	$123.52	3.197%	$127.4689	$127.47	$127.45	$127.50
Purchase #5	$177.38	13.151%	$200.7072	$200.71	$200.70	$200.70
Purchase #6	$205.94	4.548%	$215.3062	$215.31	$215.30	$215.30
Purchase #7	$154.65	11.753%	$172.826	$172.83	$172.85	$172.80
7 purchase totals =	$1,286.36		$1,371.3426	$1,371.36	$1,371.30	$1,371.30