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	$154.92	12.268%	$173.9256	$173.93	$173.95	$173.90
Purchase #2	$17.60	12.213%	$19.7495	$19.75	$19.75	$19.70
Purchase #3	$153.28	12.851%	$172.978	$172.98	$173.00	$173.00
Purchase #4	$100.39	12.127%	$112.5643	$112.56	$112.55	$112.60
Purchase #5	$68.77	5.806%	$72.7628	$72.76	$72.75	$72.80
Purchase #6	$19.54	10.264%	$21.5456	$21.55	$21.55	$21.50
Purchase #7	$237.41	6.522%	$252.8939	$252.89	$252.90	$252.90
7 purchase totals =	$751.91		$826.4197	$826.42	$826.45	$826.40