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	$141.93	8.511%	$154.0097	$154.01	$154.00	$154.00
Purchase #2	$153.69	12.804%	$173.3685	$173.37	$173.35	$173.40
Purchase #3	$111.59	9.705%	$122.4198	$122.42	$122.40	$122.40
Purchase #4	$172.51	10.270%	$190.2268	$190.23	$190.25	$190.20
Purchase #5	$215.85	6.366%	$229.591	$229.59	$229.60	$229.60
Purchase #6	$164.60	4.773%	$172.4564	$172.46	$172.45	$172.50
Purchase #7	$9.56	12.846%	$10.7881	$10.79	$10.80	$10.80
7 purchase totals =	$969.73		$1,052.8603	$1,052.87	$1,052.85	$1,052.90