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	$131.64	7.118%	$141.0101	$141.01	$141.00	$141.00
Purchase #2	$213.86	9.634%	$234.4633	$234.46	$234.45	$234.50
Purchase #3	$116.64	9.498%	$127.7185	$127.72	$127.70	$127.70
Purchase #4	$145.52	7.728%	$156.7658	$156.77	$156.75	$156.80
Purchase #5	$133.93	4.367%	$139.7787	$139.78	$139.80	$139.80
Purchase #6	$236.25	6.702%	$252.0835	$252.08	$252.10	$252.10
Purchase #7	$127.84	12.825%	$144.2355	$144.24	$144.25	$144.20
7 purchase totals =	$1,105.68		$1,196.0554	$1,196.06	$1,196.05	$1,196.10