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	$238.92	6.734%	$255.0089	$255.01	$255.00	$255.00
Purchase #2	$73.39	6.599%	$78.233	$78.23	$78.25	$78.20
Purchase #3	$149.46	5.823%	$158.1631	$158.16	$158.15	$158.20
Purchase #4	$40.70	11.844%	$45.5205	$45.52	$45.50	$45.50
Purchase #5	$222.40	7.167%	$238.3394	$238.34	$238.35	$238.30
Purchase #6	$138.38	10.167%	$152.4491	$152.45	$152.45	$152.40
Purchase #7	$134.42	6.657%	$143.3683	$143.37	$143.35	$143.40
7 purchase totals =	$997.67		$1,071.0823	$1,071.08	$1,071.05	$1,071.00