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	$184.43	12.830%	$208.0924	$208.09	$208.10	$208.10
Purchase #2	$184.38	4.623%	$192.9039	$192.90	$192.90	$192.90
Purchase #3	$179.28	11.690%	$200.2378	$200.24	$200.25	$200.20
Purchase #4	$194.31	5.540%	$205.0748	$205.07	$205.05	$205.10
Purchase #5	$94.31	12.505%	$106.1035	$106.10	$106.10	$106.10
Purchase #6	$127.59	8.693%	$138.6814	$138.68	$138.70	$138.70
Purchase #7	$9.41	9.338%	$10.2887	$10.29	$10.30	$10.30
7 purchase totals =	$973.71		$1,061.3825	$1,061.37	$1,061.40	$1,061.40