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	$160.37	9.490%	$175.5891	$175.59	$175.60	$175.60
Purchase #2	$38.65	8.329%	$41.8692	$41.87	$41.85	$41.90
Purchase #3	$10.96	8.303%	$11.87	$11.87	$11.85	$11.90
Purchase #4	$134.38	10.375%	$148.3219	$148.32	$148.30	$148.30
Purchase #5	$177.37	4.250%	$184.9082	$184.91	$184.90	$184.90
Purchase #6	$35.97	6.267%	$38.2242	$38.22	$38.20	$38.20
Purchase #7	$111.80	6.275%	$118.8155	$118.82	$118.80	$118.80
7 purchase totals =	$669.50		$719.5981	$719.60	$719.50	$719.60