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	$199.27	7.819%	$214.8509	$214.85	$214.85	$214.90
Purchase #2	$55.39	12.566%	$62.3503	$62.35	$62.35	$62.40
Purchase #3	$158.55	12.673%	$178.643	$178.64	$178.65	$178.60
Purchase #4	$118.56	4.134%	$123.4613	$123.46	$123.45	$123.50
Purchase #5	$100.63	11.831%	$112.5355	$112.54	$112.55	$112.50
Purchase #6	$89.35	7.132%	$95.7224	$95.72	$95.70	$95.70
Purchase #7	$126.68	5.258%	$133.3408	$133.34	$133.35	$133.30
7 purchase totals =	$848.43		$920.9042	$920.90	$920.90	$920.90