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	$220.36	4.440%	$230.144	$230.14	$230.15	$230.10
Purchase #2	$132.69	12.257%	$148.9538	$148.95	$148.95	$149.00
Purchase #3	$105.64	3.422%	$109.255	$109.26	$109.25	$109.30
Purchase #4	$154.28	12.462%	$173.5064	$173.51	$173.50	$173.50
Purchase #5	$158.82	12.595%	$178.8234	$178.82	$178.80	$178.80
Purchase #6	$213.61	3.865%	$221.866	$221.87	$221.85	$221.90
Purchase #7	$113.65	13.356%	$128.8291	$128.83	$128.85	$128.80
7 purchase totals =	$1,099.05		$1,191.3777	$1,191.38	$1,191.35	$1,191.40