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	$101.85	9.650%	$111.6785	$111.68	$111.70	$111.70
Purchase #2	$102.47	3.286%	$105.8372	$105.84	$105.85	$105.80
Purchase #3	$169.27	7.183%	$181.4287	$181.43	$181.45	$181.40
Purchase #4	$219.44	13.744%	$249.5998	$249.60	$249.60	$249.60
Purchase #5	$17.82	10.246%	$19.6458	$19.65	$19.65	$19.60
Purchase #6	$214.51	10.799%	$237.6749	$237.67	$237.65	$237.70
Purchase #7	$105.87	7.406%	$113.7107	$113.71	$113.70	$113.70
7 purchase totals =	$931.23		$1,019.5756	$1,019.58	$1,019.60	$1,019.50