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	$139.66	7.663%	$150.3621	$150.36	$150.35	$150.40
Purchase #2	$198.81	3.575%	$205.9175	$205.92	$205.90	$205.90
Purchase #3	$173.49	5.707%	$183.3911	$183.39	$183.40	$183.40
Purchase #4	$12.30	9.105%	$13.4199	$13.42	$13.40	$13.40
Purchase #5	$250.75	11.175%	$278.7713	$278.77	$278.75	$278.80
Purchase #6	$117.28	8.622%	$127.3919	$127.39	$127.40	$127.40
Purchase #7	$91.63	13.389%	$103.8983	$103.90	$103.90	$103.90
7 purchase totals =	$983.92		$1,063.1521	$1,063.15	$1,063.10	$1,063.20