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	$149.57	4.823%	$156.7838	$156.78	$156.80	$156.80
Purchase #2	$154.76	11.439%	$172.463	$172.46	$172.45	$172.50
Purchase #3	$107.51	3.575%	$111.3535	$111.35	$111.35	$111.40
Purchase #4	$80.65	9.738%	$88.5037	$88.50	$88.50	$88.50
Purchase #5	$191.30	5.642%	$202.0931	$202.09	$202.10	$202.10
Purchase #6	$156.68	10.453%	$173.0578	$173.06	$173.05	$173.10
Purchase #7	$214.53	13.495%	$243.4808	$243.48	$243.50	$243.50
7 purchase totals =	$1,055.00		$1,147.7357	$1,147.72	$1,147.75	$1,147.90