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	$95.52	9.170%	$104.2792	$104.28	$104.30	$104.30
Purchase #2	$11.56	13.659%	$13.139	$13.14	$13.15	$13.10
Purchase #3	$54.62	8.749%	$59.3987	$59.40	$59.40	$59.40
Purchase #4	$70.75	9.620%	$77.5562	$77.56	$77.55	$77.60
Purchase #5	$81.70	9.162%	$89.1854	$89.19	$89.20	$89.20
Purchase #6	$50.88	10.768%	$56.3588	$56.36	$56.35	$56.40
Purchase #7	$120.67	9.602%	$132.2567	$132.26	$132.25	$132.30
7 purchase totals =	$485.70		$532.1740	$532.19	$532.20	$532.30