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	$192.83	13.816%	$219.4714	$219.47	$219.45	$219.50
Purchase #2	$56.36	11.487%	$62.8341	$62.83	$62.85	$62.80
Purchase #3	$228.37	5.758%	$241.5195	$241.52	$241.50	$241.50
Purchase #4	$247.27	7.674%	$266.2455	$266.25	$266.25	$266.20
Purchase #5	$118.86	6.302%	$126.3506	$126.35	$126.35	$126.40
Purchase #6	$221.43	7.777%	$238.6506	$238.65	$238.65	$238.70
Purchase #7	$214.86	12.854%	$242.4781	$242.48	$242.50	$242.50
7 purchase totals =	$1,279.98		$1,397.5498	$1,397.55	$1,397.55	$1,397.60