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	$218.41	9.628%	$239.4385	$239.44	$239.45	$239.40
Purchase #2	$55.71	12.377%	$62.6052	$62.61	$62.60	$62.60
Purchase #3	$33.27	5.682%	$35.1604	$35.16	$35.15	$35.20
Purchase #4	$127.51	13.443%	$144.6512	$144.65	$144.65	$144.70
Purchase #5	$165.98	7.552%	$178.5148	$178.51	$178.50	$178.50
Purchase #6	$13.41	5.137%	$14.0989	$14.10	$14.10	$14.10
Purchase #7	$34.85	8.502%	$37.8129	$37.81	$37.80	$37.80
7 purchase totals =	$649.14		$712.2819	$712.28	$712.25	$712.30