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	$158.87	6.250%	$168.7994	$168.80	$168.80	$168.80
Purchase #2	$54.85	9.147%	$59.8671	$59.87	$59.85	$59.90
Purchase #3	$160.52	7.710%	$172.8961	$172.90	$172.90	$172.90
Purchase #4	$122.75	4.262%	$127.9816	$127.98	$128.00	$128.00
Purchase #5	$224.67	12.128%	$251.918	$251.92	$251.90	$251.90
Purchase #6	$145.67	5.833%	$154.1669	$154.17	$154.15	$154.20
Purchase #7	$180.34	5.828%	$190.8502	$190.85	$190.85	$190.90
7 purchase totals =	$1,047.67		$1,126.4793	$1,126.49	$1,126.45	$1,126.60