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	$148.60	9.784%	$163.139	$163.14	$163.15	$163.10
Purchase #2	$100.66	10.369%	$111.0974	$111.10	$111.10	$111.10
Purchase #3	$235.68	12.849%	$265.9625	$265.96	$265.95	$266.00
Purchase #4	$235.73	8.752%	$256.3611	$256.36	$256.35	$256.40
Purchase #5	$26.60	4.764%	$27.8672	$27.87	$27.85	$27.90
Purchase #6	$79.52	3.137%	$82.0145	$82.01	$82.00	$82.00
Purchase #7	$153.87	12.320%	$172.8268	$172.83	$172.85	$172.80
7 purchase totals =	$980.66		$1,079.2685	$1,079.27	$1,079.25	$1,079.30