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	$78.98	3.188%	$81.4979	$81.50	$81.50	$81.50
Purchase #2	$184.88	7.554%	$198.8458	$198.85	$198.85	$198.80
Purchase #3	$153.94	9.733%	$168.923	$168.92	$168.90	$168.90
Purchase #4	$151.93	4.445%	$158.6833	$158.68	$158.70	$158.70
Purchase #5	$239.45	10.533%	$264.6713	$264.67	$264.65	$264.70
Purchase #6	$70.38	3.509%	$72.8496	$72.85	$72.85	$72.80
Purchase #7	$97.73	3.687%	$101.3333	$101.33	$101.35	$101.30
7 purchase totals =	$977.29		$1,046.8042	$1,046.80	$1,046.80	$1,046.70