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	$227.72	12.551%	$256.3011	$256.30	$256.30	$256.30
Purchase #2	$151.52	5.195%	$159.3915	$159.39	$159.40	$159.40
Purchase #3	$148.99	5.189%	$156.7211	$156.72	$156.70	$156.70
Purchase #4	$45.90	9.333%	$50.1838	$50.18	$50.20	$50.20
Purchase #5	$140.92	4.566%	$147.3544	$147.35	$147.35	$147.40
Purchase #6	$99.83	12.339%	$112.148	$112.15	$112.15	$112.10
Purchase #7	$154.55	7.438%	$166.0454	$166.05	$166.05	$166.00
7 purchase totals =	$969.43		$1,048.1453	$1,048.14	$1,048.15	$1,048.10