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	$180.89	13.367%	$205.0696	$205.07	$205.05	$205.10
Purchase #2	$98.77	6.829%	$105.515	$105.52	$105.50	$105.50
Purchase #3	$127.47	5.791%	$134.8518	$134.85	$134.85	$134.90
Purchase #4	$57.79	9.733%	$63.4147	$63.41	$63.40	$63.40
Purchase #5	$9.80	4.383%	$10.2295	$10.23	$10.25	$10.20
Purchase #6	$39.31	11.740%	$43.925	$43.93	$43.95	$43.90
Purchase #7	$194.60	5.579%	$205.4567	$205.46	$205.45	$205.50
7 purchase totals =	$708.63		$768.4623	$768.47	$768.45	$768.50