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	$101.52	12.771%	$114.4851	$114.49	$114.50	$114.50
Purchase #2	$39.88	8.771%	$43.3779	$43.38	$43.40	$43.40
Purchase #3	$76.79	13.710%	$87.3179	$87.32	$87.30	$87.30
Purchase #4	$17.35	4.549%	$18.1393	$18.14	$18.15	$18.10
Purchase #5	$142.27	9.493%	$155.7757	$155.78	$155.80	$155.80
Purchase #6	$43.77	4.383%	$45.6884	$45.69	$45.70	$45.70
Purchase #7	$17.59	10.385%	$19.4167	$19.42	$19.40	$19.40
7 purchase totals =	$439.17		$484.2010	$484.22	$484.25	$484.20