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	$246.76	6.227%	$262.1257	$262.13	$262.15	$262.10
Purchase #2	$85.55	6.259%	$90.9046	$90.90	$90.90	$90.90
Purchase #3	$11.65	10.359%	$12.8568	$12.86	$12.85	$12.90
Purchase #4	$70.42	5.468%	$74.2706	$74.27	$74.25	$74.30
Purchase #5	$86.86	4.495%	$90.7644	$90.76	$90.75	$90.80
Purchase #6	$140.32	9.109%	$153.1017	$153.10	$153.10	$153.10
Purchase #7	$183.45	5.657%	$193.8278	$193.83	$193.85	$193.80
7 purchase totals =	$825.01		$877.8516	$877.85	$877.85	$877.90