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	$159.85	3.491%	$165.4304	$165.43	$165.45	$165.40
Purchase #2	$168.45	4.233%	$175.5805	$175.58	$175.60	$175.60
Purchase #3	$150.51	3.241%	$155.388	$155.39	$155.40	$155.40
Purchase #4	$99.88	5.650%	$105.5232	$105.52	$105.50	$105.50
Purchase #5	$157.41	12.491%	$177.0721	$177.07	$177.05	$177.10
Purchase #6	$85.52	11.423%	$95.2889	$95.29	$95.30	$95.30
Purchase #7	$47.29	7.183%	$50.6868	$50.69	$50.70	$50.70
7 purchase totals =	$868.91		$924.9699	$924.97	$925.00	$925.00