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	$86.42	9.612%	$94.7267	$94.73	$94.75	$94.70
Purchase #2	$128.54	7.286%	$137.9054	$137.91	$137.90	$137.90
Purchase #3	$103.88	7.159%	$111.3168	$111.32	$111.30	$111.30
Purchase #4	$115.47	13.482%	$131.0377	$131.04	$131.05	$131.00
Purchase #5	$30.67	11.320%	$34.1418	$34.14	$34.15	$34.10
Purchase #6	$187.78	12.244%	$210.7718	$210.77	$210.75	$210.80
Purchase #7	$230.86	6.193%	$245.1572	$245.16	$245.15	$245.20
7 purchase totals =	$883.62		$965.0574	$965.07	$965.05	$965.00