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	$222.28	9.252%	$242.8453	$242.85	$242.85	$242.80
Purchase #2	$111.47	4.398%	$116.3725	$116.37	$116.35	$116.40
Purchase #3	$172.54	6.825%	$184.3159	$184.32	$184.30	$184.30
Purchase #4	$167.89	13.400%	$190.3873	$190.39	$190.40	$190.40
Purchase #5	$226.79	13.161%	$256.6378	$256.64	$256.65	$256.60
Purchase #6	$101.82	12.129%	$114.1697	$114.17	$114.15	$114.20
Purchase #7	$196.58	5.828%	$208.0367	$208.04	$208.05	$208.00
7 purchase totals =	$1,199.37		$1,312.7652	$1,312.78	$1,312.75	$1,312.70