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	$228.38	12.211%	$256.2675	$256.27	$256.25	$256.30
Purchase #2	$64.30	11.361%	$71.6051	$71.61	$71.60	$71.60
Purchase #3	$59.46	3.663%	$61.638	$61.64	$61.65	$61.60
Purchase #4	$240.29	5.103%	$252.552	$252.55	$252.55	$252.60
Purchase #5	$155.76	4.493%	$162.7583	$162.76	$162.75	$162.80
Purchase #6	$78.41	4.284%	$81.7691	$81.77	$81.75	$81.80
Purchase #7	$34.74	11.749%	$38.8216	$38.82	$38.80	$38.80
7 purchase totals =	$861.34		$925.4116	$925.42	$925.35	$925.50