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	$193.86	11.852%	$216.8363	$216.84	$216.85	$216.80
Purchase #2	$223.38	5.536%	$235.7463	$235.75	$235.75	$235.70
Purchase #3	$45.76	10.172%	$50.4147	$50.41	$50.40	$50.40
Purchase #4	$141.88	8.167%	$153.4673	$153.47	$153.45	$153.50
Purchase #5	$183.85	3.796%	$190.8289	$190.83	$190.85	$190.80
Purchase #6	$59.82	9.806%	$65.6859	$65.69	$65.70	$65.70
Purchase #7	$148.93	4.470%	$155.5872	$155.59	$155.60	$155.60
7 purchase totals =	$997.48		$1,068.5666	$1,068.58	$1,068.60	$1,068.50