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	$55.66	11.347%	$61.9757	$61.98	$62.00	$62.00
Purchase #2	$118.79	13.509%	$134.8373	$134.84	$134.85	$134.80
Purchase #3	$203.50	13.198%	$230.3579	$230.36	$230.35	$230.40
Purchase #4	$34.58	10.765%	$38.3025	$38.30	$38.30	$38.30
Purchase #5	$117.39	4.870%	$123.1069	$123.11	$123.10	$123.10
Purchase #6	$137.77	7.491%	$148.0904	$148.09	$148.10	$148.10
Purchase #7	$249.91	12.808%	$281.9185	$281.92	$281.90	$281.90
7 purchase totals =	$917.60		$1,018.5892	$1,018.60	$1,018.60	$1,018.60