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	$58.91	11.198%	$65.5067	$65.51	$65.50	$65.50
Purchase #2	$238.89	4.754%	$250.2468	$250.25	$250.25	$250.20
Purchase #3	$74.57	6.863%	$79.6877	$79.69	$79.70	$79.70
Purchase #4	$15.77	13.363%	$17.8773	$17.88	$17.90	$17.90
Purchase #5	$207.57	3.867%	$215.5967	$215.60	$215.60	$215.60
Purchase #6	$80.92	11.468%	$90.1999	$90.20	$90.20	$90.20
Purchase #7	$71.93	7.245%	$77.1413	$77.14	$77.15	$77.10
7 purchase totals =	$748.56		$796.2564	$796.27	$796.30	$796.20