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	$217.25	8.719%	$236.192	$236.19	$236.20	$236.20
Purchase #2	$151.97	4.271%	$158.4606	$158.46	$158.45	$158.50
Purchase #3	$46.54	13.113%	$52.6428	$52.64	$52.65	$52.60
Purchase #4	$173.45	8.238%	$187.7388	$187.74	$187.75	$187.70
Purchase #5	$96.48	4.156%	$100.4897	$100.49	$100.50	$100.50
Purchase #6	$180.50	5.488%	$190.4058	$190.41	$190.40	$190.40
Purchase #7	$140.63	9.237%	$153.62	$153.62	$153.60	$153.60
7 purchase totals =	$1,006.82		$1,079.5497	$1,079.55	$1,079.55	$1,079.50