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	$66.34	8.719%	$72.1242	$72.12	$72.10	$72.10
Purchase #2	$137.63	5.244%	$144.8473	$144.85	$144.85	$144.80
Purchase #3	$49.76	5.720%	$52.6063	$52.61	$52.60	$52.60
Purchase #4	$174.58	9.747%	$191.5963	$191.60	$191.60	$191.60
Purchase #5	$223.67	8.330%	$242.3017	$242.30	$242.30	$242.30
Purchase #6	$63.52	5.262%	$66.8624	$66.86	$66.85	$66.90
Purchase #7	$214.88	9.653%	$235.6224	$235.62	$235.60	$235.60
7 purchase totals =	$930.38		$1,005.9606	$1,005.96	$1,005.90	$1,005.90