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	$47.33	4.244%	$49.3387	$49.34	$49.35	$49.30
Purchase #2	$72.39	8.861%	$78.8045	$78.80	$78.80	$78.80
Purchase #3	$145.85	4.659%	$152.6452	$152.65	$152.65	$152.60
Purchase #4	$82.75	11.693%	$92.426	$92.43	$92.45	$92.40
Purchase #5	$89.27	12.187%	$100.1493	$100.15	$100.15	$100.10
Purchase #6	$136.53	13.369%	$154.7827	$154.78	$154.80	$154.80
Purchase #7	$190.68	13.208%	$215.865	$215.87	$215.85	$215.90
7 purchase totals =	$764.80		$844.0114	$844.02	$844.05	$843.90