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	$204.36	11.491%	$227.843	$227.84	$227.85	$227.80
Purchase #2	$91.37	9.602%	$100.1433	$100.14	$100.15	$100.10
Purchase #3	$51.32	12.149%	$57.5549	$57.55	$57.55	$57.60
Purchase #4	$100.60	6.450%	$107.0887	$107.09	$107.10	$107.10
Purchase #5	$57.61	6.816%	$61.5367	$61.54	$61.55	$61.50
Purchase #6	$159.89	13.482%	$181.4464	$181.45	$181.45	$181.40
Purchase #7	$33.76	3.160%	$34.8268	$34.83	$34.85	$34.80
7 purchase totals =	$698.91		$770.4398	$770.44	$770.50	$770.30