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	$208.29	3.534%	$215.651	$215.65	$215.65	$215.70
Purchase #2	$173.45	5.643%	$183.2378	$183.24	$183.25	$183.20
Purchase #3	$70.25	8.422%	$76.1665	$76.17	$76.15	$76.20
Purchase #4	$78.87	4.361%	$82.3095	$82.31	$82.30	$82.30
Purchase #5	$153.62	6.351%	$163.3764	$163.38	$163.40	$163.40
Purchase #6	$215.30	12.187%	$241.5386	$241.54	$241.55	$241.50
Purchase #7	$51.44	6.104%	$54.5799	$54.58	$54.60	$54.60
7 purchase totals =	$951.22		$1,016.8597	$1,016.87	$1,016.90	$1,016.90