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	$214.74	8.639%	$233.2914	$233.29	$233.30	$233.30
Purchase #2	$30.30	5.702%	$32.0277	$32.03	$32.05	$32.00
Purchase #3	$246.35	13.585%	$279.8166	$279.82	$279.80	$279.80
Purchase #4	$99.74	11.732%	$111.4415	$111.44	$111.45	$111.40
Purchase #5	$19.27	10.131%	$21.2222	$21.22	$21.20	$21.20
Purchase #6	$215.89	8.167%	$233.5217	$233.52	$233.50	$233.50
Purchase #7	$194.29	3.870%	$201.809	$201.81	$201.80	$201.80
7 purchase totals =	$1,020.58		$1,113.1301	$1,113.13	$1,113.10	$1,113.00