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	$104.45	6.434%	$111.1703	$111.17	$111.15	$111.20
Purchase #2	$154.32	12.657%	$173.8523	$173.85	$173.85	$173.90
Purchase #3	$104.72	6.343%	$111.3624	$111.36	$111.35	$111.40
Purchase #4	$179.35	13.143%	$202.922	$202.92	$202.90	$202.90
Purchase #5	$155.73	10.695%	$172.3853	$172.39	$172.40	$172.40
Purchase #6	$43.70	4.545%	$45.6862	$45.69	$45.70	$45.70
Purchase #7	$153.83	5.823%	$162.7875	$162.79	$162.80	$162.80
7 purchase totals =	$896.10		$980.1660	$980.17	$980.15	$980.30