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	$168.69	13.874%	$192.0941	$192.09	$192.10	$192.10
Purchase #2	$32.42	3.583%	$33.5816	$33.58	$33.60	$33.60
Purchase #3	$164.99	11.540%	$184.0298	$184.03	$184.05	$184.00
Purchase #4	$6.27	6.678%	$6.6887	$6.69	$6.70	$6.70
Purchase #5	$79.82	12.111%	$89.487	$89.49	$89.50	$89.50
Purchase #6	$99.54	13.246%	$112.7251	$112.73	$112.75	$112.70
Purchase #7	$241.81	8.489%	$262.3373	$262.34	$262.35	$262.30
7 purchase totals =	$793.54		$880.9436	$880.95	$881.05	$880.90