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	$60.45	8.163%	$65.3845	$65.38	$65.40	$65.40
Purchase #2	$48.39	8.218%	$52.3667	$52.37	$52.35	$52.40
Purchase #3	$127.52	13.839%	$145.1675	$145.17	$145.15	$145.20
Purchase #4	$172.46	4.792%	$180.7243	$180.72	$180.70	$180.70
Purchase #5	$157.63	5.658%	$166.5487	$166.55	$166.55	$166.50
Purchase #6	$225.39	12.858%	$254.3706	$254.37	$254.35	$254.40
Purchase #7	$106.77	5.610%	$112.7598	$112.76	$112.75	$112.80
7 purchase totals =	$898.61		$977.3221	$977.32	$977.25	$977.40