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	$200.96	3.868%	$208.7331	$208.73	$208.75	$208.70
Purchase #2	$49.82	6.249%	$52.9333	$52.93	$52.95	$52.90
Purchase #3	$165.73	6.756%	$176.9267	$176.93	$176.95	$176.90
Purchase #4	$223.83	3.370%	$231.3731	$231.37	$231.35	$231.40
Purchase #5	$39.76	6.193%	$42.2223	$42.22	$42.20	$42.20
Purchase #6	$74.73	9.247%	$81.6403	$81.64	$81.65	$81.60
Purchase #7	$111.62	10.728%	$123.5946	$123.59	$123.60	$123.60
7 purchase totals =	$866.45		$917.4234	$917.41	$917.45	$917.30