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	$100.95	10.726%	$111.7779	$111.78	$111.80	$111.80
Purchase #2	$19.75	11.803%	$22.0811	$22.08	$22.10	$22.10
Purchase #3	$66.92	4.405%	$69.8678	$69.87	$69.85	$69.90
Purchase #4	$130.29	8.567%	$141.4519	$141.45	$141.45	$141.50
Purchase #5	$31.92	8.345%	$34.5837	$34.58	$34.60	$34.60
Purchase #6	$80.72	10.763%	$89.4079	$89.41	$89.40	$89.40
Purchase #7	$65.56	4.403%	$68.4466	$68.45	$68.45	$68.40
7 purchase totals =	$496.11		$537.6169	$537.62	$537.65	$537.70