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	$174.41	13.613%	$198.1524	$198.15	$198.15	$198.20
Purchase #2	$22.46	10.801%	$24.8859	$24.89	$24.90	$24.90
Purchase #3	$123.62	3.335%	$127.7427	$127.74	$127.75	$127.70
Purchase #4	$224.93	4.693%	$235.486	$235.49	$235.50	$235.50
Purchase #5	$250.52	5.497%	$264.2911	$264.29	$264.30	$264.30
Purchase #6	$48.77	10.551%	$53.9157	$53.92	$53.90	$53.90
Purchase #7	$63.83	3.468%	$66.0436	$66.04	$66.05	$66.00
7 purchase totals =	$908.54		$970.5174	$970.52	$970.55	$970.50