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	$214.68	11.609%	$239.6022	$239.60	$239.60	$239.60
Purchase #2	$234.68	13.695%	$266.8194	$266.82	$266.80	$266.80
Purchase #3	$19.90	6.574%	$21.2082	$21.21	$21.20	$21.20
Purchase #4	$97.99	3.590%	$101.5078	$101.51	$101.50	$101.50
Purchase #5	$104.33	7.300%	$111.9461	$111.95	$111.95	$111.90
Purchase #6	$235.93	8.758%	$256.5927	$256.59	$256.60	$256.60
Purchase #7	$137.88	5.379%	$145.2966	$145.30	$145.30	$145.30
7 purchase totals =	$1,045.39		$1,142.9730	$1,142.98	$1,142.95	$1,142.90