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	$167.38	13.633%	$190.1989	$190.20	$190.20	$190.20
Purchase #2	$70.99	3.325%	$73.3504	$73.35	$73.35	$73.40
Purchase #3	$184.31	3.595%	$190.9359	$190.94	$190.95	$190.90
Purchase #4	$186.32	6.714%	$198.8295	$198.83	$198.85	$198.80
Purchase #5	$115.94	13.384%	$131.4574	$131.46	$131.45	$131.50
Purchase #6	$34.42	11.750%	$38.4644	$38.46	$38.45	$38.50
Purchase #7	$210.58	9.550%	$230.6904	$230.69	$230.70	$230.70
7 purchase totals =	$969.94		$1,053.9269	$1,053.93	$1,053.95	$1,054.00