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	$228.75	10.178%	$252.0322	$252.03	$252.05	$252.00
Purchase #2	$34.97	9.459%	$38.2778	$38.28	$38.30	$38.30
Purchase #3	$103.45	4.857%	$108.4746	$108.47	$108.45	$108.50
Purchase #4	$133.89	5.388%	$141.104	$141.10	$141.10	$141.10
Purchase #5	$182.40	13.113%	$206.3181	$206.32	$206.30	$206.30
Purchase #6	$83.66	6.715%	$89.2778	$89.28	$89.30	$89.30
Purchase #7	$249.32	13.429%	$282.8012	$282.80	$282.80	$282.80
7 purchase totals =	$1,016.44		$1,118.2857	$1,118.28	$1,118.30	$1,118.30