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	$117.83	11.149%	$130.9669	$130.97	$130.95	$131.00
Purchase #2	$166.99	11.286%	$185.8365	$185.84	$185.85	$185.80
Purchase #3	$53.67	5.143%	$56.4302	$56.43	$56.45	$56.40
Purchase #4	$91.35	11.419%	$101.7813	$101.78	$101.80	$101.80
Purchase #5	$167.60	5.329%	$176.5314	$176.53	$176.55	$176.50
Purchase #6	$20.39	6.740%	$21.7643	$21.76	$21.75	$21.80
Purchase #7	$188.64	10.536%	$208.5151	$208.52	$208.50	$208.50
7 purchase totals =	$806.47		$881.8257	$881.83	$881.85	$881.80