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	$214.91	3.529%	$222.4942	$222.49	$222.50	$222.50
Purchase #2	$108.78	9.619%	$119.2435	$119.24	$119.25	$119.20
Purchase #3	$57.48	4.613%	$60.1316	$60.13	$60.15	$60.10
Purchase #4	$74.41	11.388%	$82.8838	$82.88	$82.90	$82.90
Purchase #5	$93.38	7.336%	$100.2304	$100.23	$100.25	$100.20
Purchase #6	$110.42	6.712%	$117.8314	$117.83	$117.85	$117.80
Purchase #7	$96.79	11.137%	$107.5695	$107.57	$107.55	$107.60
7 purchase totals =	$756.17		$810.3844	$810.37	$810.45	$810.30