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	$95.76	13.275%	$108.4721	$108.47	$108.45	$108.50
Purchase #2	$138.26	9.716%	$151.6933	$151.69	$151.70	$151.70
Purchase #3	$11.45	6.719%	$12.2193	$12.22	$12.20	$12.20
Purchase #4	$245.54	5.574%	$259.2264	$259.23	$259.25	$259.20
Purchase #5	$6.95	8.140%	$7.5157	$7.52	$7.50	$7.50
Purchase #6	$29.35	9.305%	$32.081	$32.08	$32.10	$32.10
Purchase #7	$99.58	6.292%	$105.8456	$105.85	$105.85	$105.80
7 purchase totals =	$626.89		$677.0534	$677.06	$677.05	$677.00