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	$119.57	6.868%	$127.7821	$127.78	$127.80	$127.80
Purchase #2	$137.70	7.823%	$148.4723	$148.47	$148.45	$148.50
Purchase #3	$74.46	5.568%	$78.6059	$78.61	$78.60	$78.60
Purchase #4	$73.80	13.862%	$84.0302	$84.03	$84.05	$84.00
Purchase #5	$11.70	4.547%	$12.232	$12.23	$12.25	$12.20
Purchase #6	$57.72	5.228%	$60.7376	$60.74	$60.75	$60.70
Purchase #7	$59.76	7.616%	$64.3113	$64.31	$64.30	$64.30
7 purchase totals =	$534.71		$576.1714	$576.17	$576.20	$576.10