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	$48.66	3.525%	$50.3753	$50.38	$50.40	$50.40
Purchase #2	$222.39	10.307%	$245.3117	$245.31	$245.30	$245.30
Purchase #3	$84.50	3.436%	$87.4034	$87.40	$87.40	$87.40
Purchase #4	$11.49	11.823%	$12.8485	$12.85	$12.85	$12.80
Purchase #5	$116.31	8.857%	$126.6116	$126.61	$126.60	$126.60
Purchase #6	$91.98	9.391%	$100.6178	$100.62	$100.60	$100.60
Purchase #7	$226.85	10.399%	$250.4401	$250.44	$250.45	$250.40
7 purchase totals =	$802.18		$873.6084	$873.61	$873.60	$873.50