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	$230.71	12.246%	$258.9627	$258.96	$258.95	$259.00
Purchase #2	$11.78	6.286%	$12.5205	$12.52	$12.50	$12.50
Purchase #3	$90.83	6.694%	$96.9102	$96.91	$96.90	$96.90
Purchase #4	$69.71	4.480%	$72.833	$72.83	$72.85	$72.80
Purchase #5	$74.86	4.686%	$78.3679	$78.37	$78.35	$78.40
Purchase #6	$27.45	6.276%	$29.1728	$29.17	$29.15	$29.20
Purchase #7	$232.93	8.188%	$252.0023	$252.00	$252.00	$252.00
7 purchase totals =	$738.27		$800.7694	$800.76	$800.70	$800.80