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	$132.91	13.758%	$151.1958	$151.20	$151.20	$151.20
Purchase #2	$97.65	13.761%	$111.0876	$111.09	$111.10	$111.10
Purchase #3	$39.25	13.360%	$44.4938	$44.49	$44.50	$44.50
Purchase #4	$61.72	13.647%	$70.1429	$70.14	$70.15	$70.10
Purchase #5	$106.81	8.238%	$115.609	$115.61	$115.60	$115.60
Purchase #6	$107.61	12.363%	$120.9138	$120.91	$120.90	$120.90
Purchase #7	$93.48	11.437%	$104.1713	$104.17	$104.15	$104.20
7 purchase totals =	$639.43		$717.6142	$717.61	$717.60	$717.60