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	$101.82	9.268%	$111.2567	$111.26	$111.25	$111.30
Purchase #2	$94.63	11.466%	$105.4803	$105.48	$105.50	$105.50
Purchase #3	$29.97	3.575%	$31.0414	$31.04	$31.05	$31.00
Purchase #4	$74.85	3.506%	$77.4742	$77.47	$77.45	$77.50
Purchase #5	$80.32	11.472%	$89.5343	$89.53	$89.55	$89.50
Purchase #6	$224.40	13.684%	$255.1069	$255.11	$255.10	$255.10
Purchase #7	$19.47	5.832%	$20.6055	$20.61	$20.60	$20.60
7 purchase totals =	$625.46		$690.4993	$690.50	$690.50	$690.50