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	$85.61	12.614%	$96.4088	$96.41	$96.40	$96.40
Purchase #2	$186.47	10.382%	$205.8293	$205.83	$205.85	$205.80
Purchase #3	$6.37	11.733%	$7.1174	$7.12	$7.10	$7.10
Purchase #4	$28.28	10.436%	$31.2313	$31.23	$31.25	$31.20
Purchase #5	$92.27	3.466%	$95.4681	$95.47	$95.45	$95.50
Purchase #6	$200.71	5.839%	$212.4295	$212.43	$212.45	$212.40
Purchase #7	$197.95	11.208%	$220.1362	$220.14	$220.15	$220.10
7 purchase totals =	$797.66		$868.6206	$868.63	$868.65	$868.50