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	$178.67	9.369%	$195.4096	$195.41	$195.40	$195.40
Purchase #2	$116.61	10.422%	$128.7631	$128.76	$128.75	$128.80
Purchase #3	$90.72	13.710%	$103.1577	$103.16	$103.15	$103.20
Purchase #4	$204.63	8.842%	$222.7234	$222.72	$222.70	$222.70
Purchase #5	$99.84	12.778%	$112.5976	$112.60	$112.60	$112.60
Purchase #6	$177.45	12.469%	$199.5762	$199.58	$199.60	$199.60
Purchase #7	$51.26	11.604%	$57.2082	$57.21	$57.20	$57.20
7 purchase totals =	$919.18		$1,019.4358	$1,019.44	$1,019.40	$1,019.50