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	$58.96	8.146%	$63.7629	$63.76	$63.75	$63.80
Purchase #2	$58.31	10.649%	$64.5194	$64.52	$64.50	$64.50
Purchase #3	$62.65	5.650%	$66.1897	$66.19	$66.20	$66.20
Purchase #4	$219.79	5.210%	$231.2411	$231.24	$231.25	$231.20
Purchase #5	$60.28	10.332%	$66.5081	$66.51	$66.50	$66.50
Purchase #6	$49.42	10.372%	$54.5458	$54.55	$54.55	$54.50
Purchase #7	$249.82	10.333%	$275.6339	$275.63	$275.65	$275.60
7 purchase totals =	$759.23		$822.4009	$822.40	$822.40	$822.30