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	$12.31	10.794%	$13.6387	$13.64	$13.65	$13.60
Purchase #2	$12.28	8.225%	$13.29	$13.29	$13.30	$13.30
Purchase #3	$67.47	7.252%	$72.3629	$72.36	$72.35	$72.40
Purchase #4	$69.55	9.624%	$76.2435	$76.24	$76.25	$76.20
Purchase #5	$166.95	3.381%	$172.5946	$172.59	$172.60	$172.60
Purchase #6	$68.61	3.376%	$70.9263	$70.93	$70.95	$70.90
Purchase #7	$111.32	4.231%	$116.0299	$116.03	$116.05	$116.00
7 purchase totals =	$508.49		$535.0859	$535.08	$535.15	$535.00