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	$101.83	9.661%	$111.6678	$111.67	$111.65	$111.70
Purchase #2	$9.46	9.168%	$10.3273	$10.33	$10.35	$10.30
Purchase #3	$158.97	11.295%	$176.9257	$176.93	$176.95	$176.90
Purchase #4	$49.52	10.113%	$54.528	$54.53	$54.55	$54.50
Purchase #5	$132.85	7.496%	$142.8084	$142.81	$142.80	$142.80
Purchase #6	$102.45	12.563%	$115.3208	$115.32	$115.30	$115.30
Purchase #7	$205.33	5.793%	$217.2248	$217.22	$217.20	$217.20
7 purchase totals =	$760.41		$828.8028	$828.81	$828.80	$828.70