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	$100.86	7.490%	$108.4144	$108.41	$108.40	$108.40
Purchase #2	$130.32	5.115%	$136.9859	$136.99	$137.00	$137.00
Purchase #3	$179.86	9.304%	$196.5942	$196.59	$196.60	$196.60
Purchase #4	$248.58	4.717%	$260.3055	$260.31	$260.30	$260.30
Purchase #5	$132.93	9.810%	$145.9704	$145.97	$145.95	$146.00
Purchase #6	$104.39	13.162%	$118.1298	$118.13	$118.15	$118.10
Purchase #7	$104.75	6.407%	$111.4613	$111.46	$111.45	$111.50
7 purchase totals =	$1,001.69		$1,077.8615	$1,077.86	$1,077.85	$1,077.90