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	$192.61	13.659%	$218.9186	$218.92	$218.90	$218.90
Purchase #2	$99.37	11.838%	$111.1334	$111.13	$111.15	$111.10
Purchase #3	$207.33	11.617%	$231.4155	$231.42	$231.40	$231.40
Purchase #4	$148.87	8.388%	$161.3572	$161.36	$161.35	$161.40
Purchase #5	$176.32	7.243%	$189.0909	$189.09	$189.10	$189.10
Purchase #6	$112.95	5.791%	$119.4909	$119.49	$119.50	$119.50
Purchase #7	$97.56	7.647%	$105.0204	$105.02	$105.00	$105.00
7 purchase totals =	$1,035.01		$1,136.4269	$1,136.43	$1,136.40	$1,136.40