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	$144.64	4.651%	$151.3672	$151.37	$151.35	$151.40
Purchase #2	$233.50	9.480%	$255.6358	$255.64	$255.65	$255.60
Purchase #3	$66.35	9.683%	$72.7747	$72.77	$72.75	$72.80
Purchase #4	$111.75	13.577%	$126.9223	$126.92	$126.90	$126.90
Purchase #5	$188.78	12.813%	$212.9684	$212.97	$212.95	$213.00
Purchase #6	$234.43	4.581%	$245.1692	$245.17	$245.15	$245.20
Purchase #7	$231.92	11.863%	$259.4327	$259.43	$259.45	$259.40
7 purchase totals =	$1,211.37		$1,324.2703	$1,324.27	$1,324.20	$1,324.30