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	$176.38	13.573%	$200.3201	$200.32	$200.30	$200.30
Purchase #2	$143.50	7.417%	$154.1434	$154.14	$154.15	$154.10
Purchase #3	$132.31	6.861%	$141.3878	$141.39	$141.40	$141.40
Purchase #4	$169.28	11.403%	$188.583	$188.58	$188.60	$188.60
Purchase #5	$48.85	8.220%	$52.8655	$52.87	$52.85	$52.90
Purchase #6	$28.71	10.765%	$31.8006	$31.80	$31.80	$31.80
Purchase #7	$11.95	3.737%	$12.3966	$12.40	$12.40	$12.40
7 purchase totals =	$710.98		$781.4970	$781.50	$781.50	$781.50