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	$196.59	4.862%	$206.1482	$206.15	$206.15	$206.10
Purchase #2	$29.94	5.551%	$31.602	$31.60	$31.60	$31.60
Purchase #3	$65.97	9.416%	$72.1817	$72.18	$72.20	$72.20
Purchase #4	$100.44	11.162%	$111.6511	$111.65	$111.65	$111.70
Purchase #5	$9.75	6.823%	$10.4152	$10.42	$10.40	$10.40
Purchase #6	$188.57	5.688%	$199.2959	$199.30	$199.30	$199.30
Purchase #7	$53.49	10.501%	$59.107	$59.11	$59.10	$59.10
7 purchase totals =	$644.75		$690.4011	$690.41	$690.40	$690.40