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	$190.25	5.286%	$200.3066	$200.31	$200.30	$200.30
Purchase #2	$139.25	8.856%	$151.582	$151.58	$151.60	$151.60
Purchase #3	$65.76	3.177%	$67.8492	$67.85	$67.85	$67.80
Purchase #4	$178.90	11.183%	$198.9064	$198.91	$198.90	$198.90
Purchase #5	$117.72	10.801%	$130.4349	$130.43	$130.45	$130.40
Purchase #6	$222.75	3.535%	$230.6242	$230.62	$230.60	$230.60
Purchase #7	$231.82	6.434%	$246.7353	$246.74	$246.75	$246.70
7 purchase totals =	$1,146.45		$1,226.4386	$1,226.44	$1,226.45	$1,226.30