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	$117.50	12.478%	$132.1617	$132.16	$132.15	$132.20
Purchase #2	$151.44	7.230%	$162.3891	$162.39	$162.40	$162.40
Purchase #3	$19.54	9.306%	$21.3584	$21.36	$21.35	$21.40
Purchase #4	$126.52	6.396%	$134.6122	$134.61	$134.60	$134.60
Purchase #5	$55.84	12.267%	$62.6899	$62.69	$62.70	$62.70
Purchase #6	$166.32	12.105%	$186.453	$186.45	$186.45	$186.50
Purchase #7	$175.78	6.286%	$186.8295	$186.83	$186.85	$186.80
7 purchase totals =	$812.94		$886.4938	$886.49	$886.50	$886.60