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	$238.90	6.737%	$254.9947	$254.99	$255.00	$255.00
Purchase #2	$146.45	8.212%	$158.4765	$158.48	$158.50	$158.50
Purchase #3	$205.52	9.746%	$225.55	$225.55	$225.55	$225.60
Purchase #4	$22.42	9.641%	$24.5815	$24.58	$24.60	$24.60
Purchase #5	$40.59	3.705%	$42.0939	$42.09	$42.10	$42.10
Purchase #6	$234.72	10.651%	$259.72	$259.72	$259.70	$259.70
Purchase #7	$127.44	4.513%	$133.1914	$133.19	$133.20	$133.20
7 purchase totals =	$1,016.04		$1,098.6080	$1,098.60	$1,098.65	$1,098.70