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	$95.88	4.243%	$99.9482	$99.95	$99.95	$99.90
Purchase #2	$177.43	9.371%	$194.057	$194.06	$194.05	$194.10
Purchase #3	$57.68	9.173%	$62.971	$62.97	$62.95	$63.00
Purchase #4	$178.87	6.713%	$190.8775	$190.88	$190.90	$190.90
Purchase #5	$62.45	12.646%	$70.3474	$70.35	$70.35	$70.30
Purchase #6	$113.67	12.505%	$127.8844	$127.88	$127.90	$127.90
Purchase #7	$209.58	5.700%	$221.5261	$221.53	$221.55	$221.50
7 purchase totals =	$895.56		$967.6116	$967.62	$967.65	$967.60