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	$95.54	10.269%	$105.351	$105.35	$105.35	$105.40
Purchase #2	$127.27	3.865%	$132.189	$132.19	$132.20	$132.20
Purchase #3	$230.71	11.152%	$256.4388	$256.44	$256.45	$256.40
Purchase #4	$99.37	8.832%	$108.1464	$108.15	$108.15	$108.10
Purchase #5	$79.63	12.434%	$89.5312	$89.53	$89.55	$89.50
Purchase #6	$77.49	4.499%	$80.9763	$80.98	$81.00	$81.00
Purchase #7	$120.42	12.810%	$135.8458	$135.85	$135.85	$135.80
7 purchase totals =	$830.43		$908.4785	$908.49	$908.55	$908.40