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	$230.40	3.317%	$238.0424	$238.04	$238.05	$238.00
Purchase #2	$47.39	10.625%	$52.4252	$52.43	$52.45	$52.40
Purchase #3	$94.94	5.120%	$99.8009	$99.80	$99.80	$99.80
Purchase #4	$154.55	4.666%	$161.7613	$161.76	$161.75	$161.80
Purchase #5	$236.88	13.609%	$269.117	$269.12	$269.10	$269.10
Purchase #6	$89.52	13.492%	$101.598	$101.60	$101.60	$101.60
Purchase #7	$79.84	4.672%	$83.5701	$83.57	$83.55	$83.60
7 purchase totals =	$933.52		$1,006.3149	$1,006.32	$1,006.30	$1,006.30