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	$173.94	11.616%	$194.1449	$194.14	$194.15	$194.10
Purchase #2	$16.57	11.109%	$18.4108	$18.41	$18.40	$18.40
Purchase #3	$225.50	10.237%	$248.5844	$248.58	$248.60	$248.60
Purchase #4	$98.28	7.594%	$105.7434	$105.74	$105.75	$105.70
Purchase #5	$158.85	4.260%	$165.617	$165.62	$165.60	$165.60
Purchase #6	$70.43	13.453%	$79.9049	$79.90	$79.90	$79.90
Purchase #7	$243.29	13.247%	$275.5186	$275.52	$275.50	$275.50
7 purchase totals =	$986.86		$1,087.9240	$1,087.91	$1,087.90	$1,087.80