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	$140.61	10.823%	$155.8282	$155.83	$155.85	$155.80
Purchase #2	$54.85	9.560%	$60.0937	$60.09	$60.10	$60.10
Purchase #3	$162.82	11.698%	$181.8667	$181.87	$181.85	$181.90
Purchase #4	$140.30	4.691%	$146.8815	$146.88	$146.90	$146.90
Purchase #5	$87.88	11.365%	$97.8676	$97.87	$97.85	$97.90
Purchase #6	$241.40	9.819%	$265.1031	$265.10	$265.10	$265.10
Purchase #7	$148.77	6.829%	$158.9295	$158.93	$158.95	$158.90
7 purchase totals =	$976.63		$1,066.5703	$1,066.57	$1,066.60	$1,066.60