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	$186.40	5.382%	$196.432	$196.43	$196.45	$196.40
Purchase #2	$152.31	3.297%	$157.3317	$157.33	$157.35	$157.30
Purchase #3	$132.57	5.703%	$140.1305	$140.13	$140.15	$140.10
Purchase #4	$230.70	10.194%	$254.2176	$254.22	$254.20	$254.20
Purchase #5	$205.71	8.221%	$222.6214	$222.62	$222.60	$222.60
Purchase #6	$45.68	10.873%	$50.6468	$50.65	$50.65	$50.60
Purchase #7	$122.47	12.223%	$137.4395	$137.44	$137.45	$137.40
7 purchase totals =	$1,075.84		$1,158.8195	$1,158.82	$1,158.85	$1,158.60