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	$241.75	5.671%	$255.4596	$255.46	$255.45	$255.50
Purchase #2	$188.76	11.432%	$210.339	$210.34	$210.35	$210.30
Purchase #3	$101.37	10.434%	$111.9469	$111.95	$111.95	$111.90
Purchase #4	$48.38	5.564%	$51.0719	$51.07	$51.05	$51.10
Purchase #5	$5.55	8.190%	$6.0045	$6.00	$6.00	$6.00
Purchase #6	$124.96	5.686%	$132.0652	$132.07	$132.05	$132.10
Purchase #7	$95.47	4.531%	$99.7957	$99.80	$99.80	$99.80
7 purchase totals =	$806.24		$866.6828	$866.69	$866.65	$866.70