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	$20.49	13.294%	$23.2139	$23.21	$23.20	$23.20
Purchase #2	$100.99	10.564%	$111.6586	$111.66	$111.65	$111.70
Purchase #3	$61.32	5.367%	$64.611	$64.61	$64.60	$64.60
Purchase #4	$114.40	3.860%	$118.8158	$118.82	$118.80	$118.80
Purchase #5	$198.78	11.873%	$222.3811	$222.38	$222.40	$222.40
Purchase #6	$6.83	11.705%	$7.6295	$7.63	$7.65	$7.60
Purchase #7	$149.85	12.179%	$168.1002	$168.10	$168.10	$168.10
7 purchase totals =	$652.66		$716.4101	$716.41	$716.40	$716.40