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	$178.40	5.416%	$188.0621	$188.06	$188.05	$188.10
Purchase #2	$105.64	10.243%	$116.4607	$116.46	$116.45	$116.50
Purchase #3	$184.50	3.196%	$190.3966	$190.40	$190.40	$190.40
Purchase #4	$164.56	8.389%	$178.3649	$178.36	$178.35	$178.40
Purchase #5	$136.42	8.804%	$148.4304	$148.43	$148.45	$148.40
Purchase #6	$205.44	12.176%	$230.4544	$230.45	$230.45	$230.50
Purchase #7	$105.91	5.562%	$111.8007	$111.80	$111.80	$111.80
7 purchase totals =	$1,080.87		$1,163.9698	$1,163.96	$1,163.95	$1,164.10