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	$66.29	6.103%	$70.3357	$70.34	$70.35	$70.30
Purchase #2	$17.48	4.723%	$18.3056	$18.31	$18.30	$18.30
Purchase #3	$117.62	4.681%	$123.1258	$123.13	$123.15	$123.10
Purchase #4	$125.73	11.246%	$139.8696	$139.87	$139.85	$139.90
Purchase #5	$118.70	8.214%	$128.45	$128.45	$128.45	$128.50
Purchase #6	$167.80	3.168%	$173.1159	$173.12	$173.10	$173.10
Purchase #7	$60.99	8.769%	$66.3382	$66.34	$66.35	$66.30
7 purchase totals =	$674.61		$719.5408	$719.56	$719.55	$719.50