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	$179.26	13.665%	$203.7559	$203.76	$203.75	$203.80
Purchase #2	$138.50	10.251%	$152.6976	$152.70	$152.70	$152.70
Purchase #3	$250.55	5.567%	$264.4981	$264.50	$264.50	$264.50
Purchase #4	$117.84	12.504%	$132.5747	$132.57	$132.55	$132.60
Purchase #5	$145.51	4.213%	$151.6403	$151.64	$151.65	$151.60
Purchase #6	$185.60	7.166%	$198.9001	$198.90	$198.90	$198.90
Purchase #7	$105.57	5.866%	$111.7627	$111.76	$111.75	$111.80
7 purchase totals =	$1,122.83		$1,215.8294	$1,215.83	$1,215.80	$1,215.90