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	$214.91	13.854%	$244.6836	$244.68	$244.70	$244.70
Purchase #2	$167.42	4.184%	$174.4249	$174.42	$174.40	$174.40
Purchase #3	$25.40	8.141%	$27.4678	$27.47	$27.45	$27.50
Purchase #4	$153.37	8.126%	$165.8328	$165.83	$165.85	$165.80
Purchase #5	$137.47	5.377%	$144.8618	$144.86	$144.85	$144.90
Purchase #6	$184.67	11.234%	$205.4158	$205.42	$205.40	$205.40
Purchase #7	$11.93	11.206%	$13.2669	$13.27	$13.25	$13.30
7 purchase totals =	$895.17		$975.9536	$975.95	$975.90	$976.00