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	$214.56	10.246%	$236.5438	$236.54	$236.55	$236.50
Purchase #2	$98.61	13.238%	$111.664	$111.66	$111.65	$111.70
Purchase #3	$124.93	13.667%	$142.0042	$142.00	$142.00	$142.00
Purchase #4	$100.94	4.299%	$105.2794	$105.28	$105.30	$105.30
Purchase #5	$224.56	7.589%	$241.6019	$241.60	$241.60	$241.60
Purchase #6	$190.48	12.839%	$214.9357	$214.94	$214.95	$214.90
Purchase #7	$219.41	6.505%	$233.6826	$233.68	$233.70	$233.70
7 purchase totals =	$1,173.49		$1,285.7116	$1,285.70	$1,285.75	$1,285.70