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	$105.29	6.318%	$111.9422	$111.94	$111.95	$111.90
Purchase #2	$160.91	9.143%	$175.622	$175.62	$175.60	$175.60
Purchase #3	$203.27	5.501%	$214.4519	$214.45	$214.45	$214.50
Purchase #4	$28.32	9.815%	$31.0996	$31.10	$31.10	$31.10
Purchase #5	$184.40	13.419%	$209.1446	$209.14	$209.15	$209.10
Purchase #6	$105.42	10.526%	$116.5165	$116.52	$116.50	$116.50
Purchase #7	$26.49	4.783%	$27.757	$27.76	$27.75	$27.80
7 purchase totals =	$814.10		$886.5338	$886.53	$886.50	$886.50