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	$39.82	9.224%	$43.493	$43.49	$43.50	$43.50
Purchase #2	$162.85	7.104%	$174.4189	$174.42	$174.40	$174.40
Purchase #3	$242.50	5.218%	$255.1537	$255.15	$255.15	$255.20
Purchase #4	$217.68	8.651%	$236.5115	$236.51	$236.50	$236.50
Purchase #5	$224.42	5.636%	$237.0683	$237.07	$237.05	$237.10
Purchase #6	$43.63	10.363%	$48.1514	$48.15	$48.15	$48.20
Purchase #7	$153.44	12.654%	$172.8563	$172.86	$172.85	$172.90
7 purchase totals =	$1,084.34		$1,167.6531	$1,167.65	$1,167.60	$1,167.80