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	$218.88	8.342%	$237.139	$237.14	$237.15	$237.10
Purchase #2	$233.70	7.566%	$251.3817	$251.38	$251.40	$251.40
Purchase #3	$98.37	5.499%	$103.7794	$103.78	$103.80	$103.80
Purchase #4	$181.73	10.554%	$200.9098	$200.91	$200.90	$200.90
Purchase #5	$51.84	5.440%	$54.6601	$54.66	$54.65	$54.70
Purchase #6	$149.77	11.113%	$166.4139	$166.41	$166.40	$166.40
Purchase #7	$146.51	8.301%	$158.6718	$158.67	$158.65	$158.70
7 purchase totals =	$1,080.80		$1,172.9557	$1,172.95	$1,172.95	$1,173.00