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	$70.57	9.523%	$77.2904	$77.29	$77.30	$77.30
Purchase #2	$51.92	5.592%	$54.8234	$54.82	$54.80	$54.80
Purchase #3	$100.69	4.332%	$105.0519	$105.05	$105.05	$105.10
Purchase #4	$133.52	11.127%	$148.3768	$148.38	$148.40	$148.40
Purchase #5	$105.30	6.311%	$111.9455	$111.95	$111.95	$111.90
Purchase #6	$69.81	13.621%	$79.3188	$79.32	$79.30	$79.30
Purchase #7	$143.32	5.579%	$151.3158	$151.32	$151.30	$151.30
7 purchase totals =	$675.13		$728.1226	$728.13	$728.10	$728.10