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	$178.46	6.642%	$190.3133	$190.31	$190.30	$190.30
Purchase #2	$51.54	10.389%	$56.8945	$56.89	$56.90	$56.90
Purchase #3	$183.43	7.189%	$196.6168	$196.62	$196.60	$196.60
Purchase #4	$37.76	3.243%	$38.9846	$38.98	$39.00	$39.00
Purchase #5	$165.27	4.833%	$173.2575	$173.26	$173.25	$173.30
Purchase #6	$56.72	12.197%	$63.6381	$63.64	$63.65	$63.60
Purchase #7	$58.84	4.516%	$61.4972	$61.50	$61.50	$61.50
7 purchase totals =	$732.02		$781.2020	$781.20	$781.20	$781.20