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	$71.56	3.584%	$74.1247	$74.12	$74.10	$74.10
Purchase #2	$95.62	10.714%	$105.8647	$105.86	$105.85	$105.90
Purchase #3	$194.52	12.212%	$218.2748	$218.27	$218.25	$218.30
Purchase #4	$103.95	12.180%	$116.6111	$116.61	$116.60	$116.60
Purchase #5	$214.41	9.857%	$235.5444	$235.54	$235.55	$235.50
Purchase #6	$175.56	3.527%	$181.752	$181.75	$181.75	$181.80
Purchase #7	$122.61	5.771%	$129.6858	$129.69	$129.70	$129.70
7 purchase totals =	$978.23		$1,061.8575	$1,061.84	$1,061.80	$1,061.90