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	$232.84	8.486%	$252.5988	$252.60	$252.60	$252.60
Purchase #2	$154.60	4.431%	$161.4503	$161.45	$161.45	$161.50
Purchase #3	$123.28	3.245%	$127.2804	$127.28	$127.30	$127.30
Purchase #4	$53.32	9.810%	$58.5507	$58.55	$58.55	$58.60
Purchase #5	$106.99	11.626%	$119.4287	$119.43	$119.45	$119.40
Purchase #6	$188.31	4.174%	$196.1701	$196.17	$196.15	$196.20
Purchase #7	$211.55	6.734%	$225.7958	$225.80	$225.80	$225.80
7 purchase totals =	$1,070.89		$1,141.2748	$1,141.28	$1,141.30	$1,141.40