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	$71.38	8.608%	$77.5244	$77.52	$77.50	$77.50
Purchase #2	$170.96	12.404%	$192.1659	$192.17	$192.15	$192.20
Purchase #3	$26.93	9.158%	$29.3962	$29.40	$29.40	$29.40
Purchase #4	$231.95	10.241%	$255.704	$255.70	$255.70	$255.70
Purchase #5	$101.82	9.112%	$111.0978	$111.10	$111.10	$111.10
Purchase #6	$10.98	5.557%	$11.5902	$11.59	$11.60	$11.60
Purchase #7	$129.80	11.475%	$144.6946	$144.69	$144.70	$144.70
7 purchase totals =	$743.82		$822.1731	$822.17	$822.15	$822.20