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	$167.33	5.293%	$176.1868	$176.19	$176.20	$176.20
Purchase #2	$153.96	10.812%	$170.6062	$170.61	$170.60	$170.60
Purchase #3	$65.32	10.733%	$72.3308	$72.33	$72.35	$72.30
Purchase #4	$29.83	7.724%	$32.1341	$32.13	$32.15	$32.10
Purchase #5	$139.82	3.712%	$145.0101	$145.01	$145.00	$145.00
Purchase #6	$32.54	10.298%	$35.891	$35.89	$35.90	$35.90
Purchase #7	$163.75	5.754%	$173.1722	$173.17	$173.15	$173.20
7 purchase totals =	$752.55		$805.3312	$805.33	$805.35	$805.30