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	$162.36	13.241%	$183.8581	$183.86	$183.85	$183.90
Purchase #2	$138.98	9.421%	$152.0733	$152.07	$152.05	$152.10
Purchase #3	$134.52	3.637%	$139.4125	$139.41	$139.40	$139.40
Purchase #4	$49.42	6.858%	$52.8092	$52.81	$52.80	$52.80
Purchase #5	$127.65	13.623%	$145.0398	$145.04	$145.05	$145.00
Purchase #6	$102.91	8.750%	$111.9146	$111.91	$111.90	$111.90
Purchase #7	$239.83	8.586%	$260.4218	$260.42	$260.40	$260.40
7 purchase totals =	$955.67		$1,045.5293	$1,045.52	$1,045.45	$1,045.50