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	$153.61	13.640%	$174.5624	$174.56	$174.55	$174.60
Purchase #2	$45.85	5.813%	$48.5153	$48.52	$48.50	$48.50
Purchase #3	$157.85	9.592%	$172.991	$172.99	$173.00	$173.00
Purchase #4	$140.71	7.551%	$151.335	$151.34	$151.35	$151.30
Purchase #5	$199.77	13.516%	$226.7709	$226.77	$226.75	$226.80
Purchase #6	$145.78	11.297%	$162.2488	$162.25	$162.25	$162.20
Purchase #7	$197.53	5.369%	$208.1354	$208.14	$208.15	$208.10
7 purchase totals =	$1,041.10		$1,144.5588	$1,144.57	$1,144.55	$1,144.50