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	$233.27	8.451%	$252.9836	$252.98	$253.00	$253.00
Purchase #2	$127.53	5.163%	$134.1144	$134.11	$134.10	$134.10
Purchase #3	$89.61	6.314%	$95.268	$95.27	$95.25	$95.30
Purchase #4	$78.58	13.855%	$89.4673	$89.47	$89.45	$89.50
Purchase #5	$37.32	6.583%	$39.7768	$39.78	$39.80	$39.80
Purchase #6	$102.28	13.521%	$116.1093	$116.11	$116.10	$116.10
Purchase #7	$144.82	9.217%	$158.1681	$158.17	$158.15	$158.20
7 purchase totals =	$813.41		$885.8875	$885.89	$885.85	$886.00