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	$35.85	8.636%	$38.946	$38.95	$38.95	$38.90
Purchase #2	$57.61	11.147%	$64.0318	$64.03	$64.05	$64.00
Purchase #3	$217.27	5.340%	$228.8722	$228.87	$228.85	$228.90
Purchase #4	$195.55	12.205%	$219.4169	$219.42	$219.40	$219.40
Purchase #5	$143.82	5.190%	$151.2843	$151.28	$151.30	$151.30
Purchase #6	$146.47	5.585%	$154.6503	$154.65	$154.65	$154.70
Purchase #7	$221.90	5.687%	$234.5195	$234.52	$234.50	$234.50
7 purchase totals =	$1,018.47		$1,091.7210	$1,091.72	$1,091.70	$1,091.70