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	$86.92	5.575%	$91.7658	$91.77	$91.75	$91.80
Purchase #2	$90.37	11.182%	$100.4752	$100.48	$100.50	$100.50
Purchase #3	$60.42	11.286%	$67.239	$67.24	$67.25	$67.20
Purchase #4	$139.30	13.585%	$158.2239	$158.22	$158.20	$158.20
Purchase #5	$155.84	3.225%	$160.8658	$160.87	$160.85	$160.90
Purchase #6	$62.30	7.623%	$67.0491	$67.05	$67.05	$67.00
Purchase #7	$105.73	9.357%	$115.6232	$115.62	$115.60	$115.60
7 purchase totals =	$700.88		$761.2420	$761.25	$761.20	$761.20