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	$61.91	10.784%	$68.5864	$68.59	$68.60	$68.60
Purchase #2	$80.69	5.845%	$85.4063	$85.41	$85.40	$85.40
Purchase #3	$73.99	4.862%	$77.5874	$77.59	$77.60	$77.60
Purchase #4	$184.72	8.494%	$200.4101	$200.41	$200.40	$200.40
Purchase #5	$133.46	9.229%	$145.777	$145.78	$145.80	$145.80
Purchase #6	$53.83	7.749%	$58.0013	$58.00	$58.00	$58.00
Purchase #7	$143.57	6.325%	$152.6508	$152.65	$152.65	$152.70
7 purchase totals =	$732.17		$788.4193	$788.43	$788.45	$788.50