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	$235.75	4.831%	$247.1391	$247.14	$247.15	$247.10
Purchase #2	$152.29	6.422%	$162.0701	$162.07	$162.05	$162.10
Purchase #3	$118.46	11.712%	$132.334	$132.33	$132.35	$132.30
Purchase #4	$21.69	13.164%	$24.5453	$24.55	$24.55	$24.50
Purchase #5	$94.95	5.857%	$100.5112	$100.51	$100.50	$100.50
Purchase #6	$18.88	12.366%	$21.2147	$21.21	$21.20	$21.20
Purchase #7	$200.88	9.324%	$219.6101	$219.61	$219.60	$219.60
7 purchase totals =	$842.90		$907.4245	$907.42	$907.40	$907.30