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	$161.67	7.299%	$173.4703	$173.47	$173.45	$173.50
Purchase #2	$102.78	4.262%	$107.1605	$107.16	$107.15	$107.20
Purchase #3	$164.85	12.852%	$186.0365	$186.04	$186.05	$186.00
Purchase #4	$230.62	13.642%	$262.0812	$262.08	$262.10	$262.10
Purchase #5	$100.83	10.379%	$111.2951	$111.30	$111.30	$111.30
Purchase #6	$148.80	7.841%	$160.4674	$160.47	$160.45	$160.50
Purchase #7	$48.69	13.474%	$55.2505	$55.25	$55.25	$55.30
7 purchase totals =	$958.24		$1,055.7615	$1,055.77	$1,055.75	$1,055.90