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	$52.35	7.634%	$56.3464	$56.35	$56.35	$56.30
Purchase #2	$29.39	13.251%	$33.2845	$33.28	$33.30	$33.30
Purchase #3	$114.96	7.527%	$123.613	$123.61	$123.60	$123.60
Purchase #4	$167.27	9.579%	$183.2928	$183.29	$183.30	$183.30
Purchase #5	$88.63	12.514%	$99.7212	$99.72	$99.70	$99.70
Purchase #6	$48.29	9.268%	$52.7655	$52.77	$52.75	$52.80
Purchase #7	$25.28	13.532%	$28.7009	$28.70	$28.70	$28.70
7 purchase totals =	$526.17		$577.7243	$577.72	$577.70	$577.70