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	$56.53	9.444%	$61.8687	$61.87	$61.85	$61.90
Purchase #2	$104.82	6.702%	$111.845	$111.85	$111.85	$111.80
Purchase #3	$49.99	5.178%	$52.5785	$52.58	$52.60	$52.60
Purchase #4	$192.58	9.749%	$211.3546	$211.35	$211.35	$211.40
Purchase #5	$179.93	3.697%	$186.582	$186.58	$186.60	$186.60
Purchase #6	$85.61	11.628%	$95.5647	$95.56	$95.55	$95.60
Purchase #7	$108.99	6.635%	$116.2215	$116.22	$116.20	$116.20
7 purchase totals =	$778.45		$836.0150	$836.01	$836.00	$836.10