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	$89.71	10.163%	$98.8272	$98.83	$98.85	$98.80
Purchase #2	$157.57	11.697%	$176.001	$176.00	$176.00	$176.00
Purchase #3	$99.88	8.839%	$108.7084	$108.71	$108.70	$108.70
Purchase #4	$151.90	10.357%	$167.6323	$167.63	$167.65	$167.60
Purchase #5	$103.84	12.586%	$116.9093	$116.91	$116.90	$116.90
Purchase #6	$230.41	6.191%	$244.6747	$244.67	$244.65	$244.70
Purchase #7	$228.39	13.665%	$259.5995	$259.60	$259.60	$259.60
7 purchase totals =	$1,061.70		$1,172.3524	$1,172.35	$1,172.35	$1,172.30