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	$179.75	5.327%	$189.3253	$189.33	$189.35	$189.30
Purchase #2	$53.76	4.675%	$56.2733	$56.27	$56.25	$56.30
Purchase #3	$179.52	10.770%	$198.8543	$198.85	$198.85	$198.90
Purchase #4	$46.32	7.650%	$49.8635	$49.86	$49.85	$49.90
Purchase #5	$247.35	3.704%	$256.5118	$256.51	$256.50	$256.50
Purchase #6	$201.76	11.236%	$224.4298	$224.43	$224.45	$224.40
Purchase #7	$50.60	5.238%	$53.2504	$53.25	$53.25	$53.30
7 purchase totals =	$959.06		$1,028.5084	$1,028.50	$1,028.50	$1,028.60