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	$192.44	6.795%	$205.5163	$205.52	$205.50	$205.50
Purchase #2	$99.96	9.412%	$109.3682	$109.37	$109.35	$109.40
Purchase #3	$244.25	6.733%	$260.6954	$260.70	$260.70	$260.70
Purchase #4	$139.90	8.104%	$151.2375	$151.24	$151.25	$151.20
Purchase #5	$53.71	7.710%	$57.851	$57.85	$57.85	$57.90
Purchase #6	$92.79	8.581%	$100.7523	$100.75	$100.75	$100.80
Purchase #7	$62.85	7.260%	$67.4129	$67.41	$67.40	$67.40
7 purchase totals =	$885.90		$952.8336	$952.84	$952.80	$952.90