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	$12.53	12.527%	$14.0996	$14.10	$14.10	$14.10
Purchase #2	$231.82	9.793%	$254.5221	$254.52	$254.50	$254.50
Purchase #3	$92.87	8.147%	$100.4361	$100.44	$100.45	$100.40
Purchase #4	$238.27	10.126%	$262.3972	$262.40	$262.40	$262.40
Purchase #5	$72.30	11.200%	$80.3976	$80.40	$80.40	$80.40
Purchase #6	$190.76	4.124%	$198.6269	$198.63	$198.65	$198.60
Purchase #7	$67.77	9.818%	$74.4237	$74.42	$74.40	$74.40
7 purchase totals =	$906.32		$984.9032	$984.91	$984.90	$984.80