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	$139.56	4.159%	$145.3643	$145.36	$145.35	$145.40
Purchase #2	$153.71	12.852%	$173.4648	$173.46	$173.45	$173.50
Purchase #3	$226.26	7.468%	$243.1571	$243.16	$243.15	$243.20
Purchase #4	$61.83	13.344%	$70.0806	$70.08	$70.10	$70.10
Purchase #5	$73.39	7.524%	$78.9119	$78.91	$78.90	$78.90
Purchase #6	$136.51	8.699%	$148.385	$148.39	$148.40	$148.40
Purchase #7	$142.26	11.486%	$158.6	$158.60	$158.60	$158.60
7 purchase totals =	$933.52		$1,017.9637	$1,017.96	$1,017.95	$1,018.10