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	$216.29	10.255%	$238.4705	$238.47	$238.45	$238.50
Purchase #2	$64.43	3.762%	$66.8539	$66.85	$66.85	$66.90
Purchase #3	$58.51	5.286%	$61.6028	$61.60	$61.60	$61.60
Purchase #4	$97.98	13.163%	$110.8771	$110.88	$110.90	$110.90
Purchase #5	$156.86	10.854%	$173.8856	$173.89	$173.90	$173.90
Purchase #6	$57.55	4.261%	$60.0022	$60.00	$60.00	$60.00
Purchase #7	$200.30	4.141%	$208.5944	$208.59	$208.60	$208.60
7 purchase totals =	$851.92		$920.2865	$920.28	$920.30	$920.40