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	$204.40	3.542%	$211.6398	$211.64	$211.65	$211.60
Purchase #2	$120.65	3.194%	$124.5036	$124.50	$124.50	$124.50
Purchase #3	$230.54	5.303%	$242.7655	$242.77	$242.75	$242.80
Purchase #4	$108.94	8.381%	$118.0703	$118.07	$118.05	$118.10
Purchase #5	$160.51	12.670%	$180.8466	$180.85	$180.85	$180.80
Purchase #6	$155.28	4.578%	$162.3887	$162.39	$162.40	$162.40
Purchase #7	$53.78	10.140%	$59.2333	$59.23	$59.25	$59.20
7 purchase totals =	$1,034.10		$1,099.4478	$1,099.45	$1,099.45	$1,099.40