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	$40.26	6.233%	$42.7694	$42.77	$42.75	$42.80
Purchase #2	$207.89	6.254%	$220.8914	$220.89	$220.90	$220.90
Purchase #3	$50.27	7.827%	$54.2046	$54.20	$54.20	$54.20
Purchase #4	$16.55	11.501%	$18.4534	$18.45	$18.45	$18.50
Purchase #5	$13.91	4.144%	$14.4864	$14.49	$14.50	$14.50
Purchase #6	$153.38	12.841%	$173.0755	$173.08	$173.10	$173.10
Purchase #7	$236.35	9.400%	$258.5669	$258.57	$258.55	$258.60
7 purchase totals =	$718.61		$782.4476	$782.45	$782.45	$782.60