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	$222.70	9.777%	$244.4734	$244.47	$244.45	$244.50
Purchase #2	$223.62	11.536%	$249.4168	$249.42	$249.40	$249.40
Purchase #3	$29.49	11.412%	$32.8554	$32.86	$32.85	$32.90
Purchase #4	$49.28	5.456%	$51.9687	$51.97	$51.95	$52.00
Purchase #5	$42.56	10.693%	$47.1109	$47.11	$47.10	$47.10
Purchase #6	$140.81	11.266%	$156.6737	$156.67	$156.65	$156.70
Purchase #7	$68.55	6.247%	$72.8323	$72.83	$72.85	$72.80
7 purchase totals =	$777.01		$855.3312	$855.33	$855.25	$855.40