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	$103.97	6.848%	$111.0899	$111.09	$111.10	$111.10
Purchase #2	$123.65	3.129%	$127.519	$127.52	$127.50	$127.50
Purchase #3	$204.55	6.240%	$217.3139	$217.31	$217.30	$217.30
Purchase #4	$233.82	9.481%	$255.9885	$255.99	$256.00	$256.00
Purchase #5	$61.97	3.654%	$64.2344	$64.23	$64.25	$64.20
Purchase #6	$137.90	3.431%	$142.6313	$142.63	$142.65	$142.60
Purchase #7	$248.76	12.624%	$280.1635	$280.16	$280.15	$280.20
7 purchase totals =	$1,114.62		$1,198.9405	$1,198.93	$1,198.95	$1,198.90