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	$216.42	6.611%	$230.7275	$230.73	$230.75	$230.70
Purchase #2	$119.41	10.789%	$132.2931	$132.29	$132.30	$132.30
Purchase #3	$87.67	13.422%	$99.4371	$99.44	$99.45	$99.40
Purchase #4	$227.30	6.252%	$241.5108	$241.51	$241.50	$241.50
Purchase #5	$126.50	3.806%	$131.3146	$131.31	$131.30	$131.30
Purchase #6	$90.53	11.207%	$100.6757	$100.68	$100.70	$100.70
Purchase #7	$92.68	5.116%	$97.4215	$97.42	$97.40	$97.40
7 purchase totals =	$960.51		$1,033.3803	$1,033.38	$1,033.40	$1,033.30