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	$79.95	9.586%	$87.614	$87.61	$87.60	$87.60
Purchase #2	$62.42	12.788%	$70.4023	$70.40	$70.40	$70.40
Purchase #3	$154.33	8.311%	$167.1564	$167.16	$167.15	$167.20
Purchase #4	$50.50	4.170%	$52.6059	$52.61	$52.60	$52.60
Purchase #5	$87.77	13.114%	$99.2802	$99.28	$99.30	$99.30
Purchase #6	$122.35	9.783%	$134.3195	$134.32	$134.30	$134.30
Purchase #7	$117.25	5.349%	$123.5217	$123.52	$123.50	$123.50
7 purchase totals =	$674.57		$734.9000	$734.90	$734.85	$734.90