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	$139.86	3.636%	$144.9453	$144.95	$144.95	$144.90
Purchase #2	$117.67	12.592%	$132.487	$132.49	$132.50	$132.50
Purchase #3	$152.78	13.411%	$173.2693	$173.27	$173.25	$173.30
Purchase #4	$248.72	7.198%	$266.6229	$266.62	$266.60	$266.60
Purchase #5	$54.44	4.348%	$56.8071	$56.81	$56.80	$56.80
Purchase #6	$123.36	3.570%	$127.764	$127.76	$127.75	$127.80
Purchase #7	$161.52	12.642%	$181.9394	$181.94	$181.95	$181.90
7 purchase totals =	$998.35		$1,083.8350	$1,083.84	$1,083.80	$1,083.80