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	$230.49	13.873%	$262.4659	$262.47	$262.45	$262.50
Purchase #2	$92.97	7.540%	$99.9799	$99.98	$100.00	$100.00
Purchase #3	$184.93	10.816%	$204.932	$204.93	$204.95	$204.90
Purchase #4	$106.42	12.314%	$119.5246	$119.52	$119.50	$119.50
Purchase #5	$133.61	4.451%	$139.557	$139.56	$139.55	$139.60
Purchase #6	$197.72	4.145%	$205.9155	$205.92	$205.90	$205.90
Purchase #7	$18.78	5.544%	$19.8212	$19.82	$19.80	$19.80
7 purchase totals =	$964.92		$1,052.1961	$1,052.20	$1,052.15	$1,052.20