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	$95.82	6.549%	$102.0953	$102.10	$102.10	$102.10
Purchase #2	$241.77	6.589%	$257.7002	$257.70	$257.70	$257.70
Purchase #3	$143.25	10.559%	$158.3758	$158.38	$158.40	$158.40
Purchase #4	$72.37	6.242%	$76.8873	$76.89	$76.90	$76.90
Purchase #5	$160.47	11.689%	$179.2273	$179.23	$179.25	$179.20
Purchase #6	$12.94	5.711%	$13.679	$13.68	$13.70	$13.70
Purchase #7	$127.83	3.146%	$131.8515	$131.85	$131.85	$131.90
7 purchase totals =	$854.45		$919.8164	$919.83	$919.90	$919.90