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	$202.39	6.453%	$215.4502	$215.45	$215.45	$215.50
Purchase #2	$121.35	4.783%	$127.1542	$127.15	$127.15	$127.20
Purchase #3	$200.27	9.723%	$219.7423	$219.74	$219.75	$219.70
Purchase #4	$83.89	10.450%	$92.6565	$92.66	$92.65	$92.70
Purchase #5	$121.28	5.154%	$127.5308	$127.53	$127.55	$127.50
Purchase #6	$127.28	3.722%	$132.0174	$132.02	$132.00	$132.00
Purchase #7	$11.40	10.310%	$12.5753	$12.58	$12.60	$12.60
7 purchase totals =	$867.86		$927.1267	$927.13	$927.15	$927.20