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	$117.87	8.454%	$127.8347	$127.83	$127.85	$127.80
Purchase #2	$38.85	8.242%	$42.052	$42.05	$42.05	$42.10
Purchase #3	$142.39	10.626%	$157.5204	$157.52	$157.50	$157.50
Purchase #4	$103.57	12.246%	$116.2532	$116.25	$116.25	$116.30
Purchase #5	$204.38	6.694%	$218.0612	$218.06	$218.05	$218.10
Purchase #6	$8.90	11.292%	$9.905	$9.91	$9.90	$9.90
Purchase #7	$227.89	4.114%	$237.2654	$237.27	$237.25	$237.30
7 purchase totals =	$843.85		$908.8919	$908.89	$908.85	$909.00