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	$75.59	8.519%	$82.0295	$82.03	$82.05	$82.00
Purchase #2	$126.53	4.649%	$132.4124	$132.41	$132.40	$132.40
Purchase #3	$166.81	8.829%	$181.5377	$181.54	$181.55	$181.50
Purchase #4	$200.70	13.184%	$227.1603	$227.16	$227.15	$227.20
Purchase #5	$112.63	5.228%	$118.5183	$118.52	$118.50	$118.50
Purchase #6	$153.52	3.456%	$158.8257	$158.83	$158.85	$158.80
Purchase #7	$98.52	9.559%	$107.9375	$107.94	$107.95	$107.90
7 purchase totals =	$934.30		$1,008.4214	$1,008.43	$1,008.45	$1,008.30