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	$105.81	5.276%	$111.3925	$111.39	$111.40	$111.40
Purchase #2	$91.32	6.871%	$97.5946	$97.59	$97.60	$97.60
Purchase #3	$118.36	11.252%	$131.6779	$131.68	$131.70	$131.70
Purchase #4	$148.72	8.444%	$161.2779	$161.28	$161.30	$161.30
Purchase #5	$199.41	11.162%	$221.6681	$221.67	$221.65	$221.70
Purchase #6	$239.43	7.449%	$257.2651	$257.27	$257.25	$257.30
Purchase #7	$238.31	7.167%	$255.3897	$255.39	$255.40	$255.40
7 purchase totals =	$1,141.36		$1,236.2658	$1,236.27	$1,236.30	$1,236.40