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	$106.65	9.108%	$116.3637	$116.36	$116.35	$116.40
Purchase #2	$152.87	13.661%	$173.7536	$173.75	$173.75	$173.80
Purchase #3	$170.59	3.709%	$176.9172	$176.92	$176.90	$176.90
Purchase #4	$19.78	6.474%	$21.0606	$21.06	$21.05	$21.10
Purchase #5	$178.25	10.381%	$196.7541	$196.75	$196.75	$196.80
Purchase #6	$152.69	4.273%	$159.2144	$159.21	$159.20	$159.20
Purchase #7	$215.39	8.461%	$233.6141	$233.61	$233.60	$233.60
7 purchase totals =	$996.22		$1,077.6777	$1,077.66	$1,077.60	$1,077.80