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	$178.97	9.523%	$196.0133	$196.01	$196.00	$196.00
Purchase #2	$22.50	12.477%	$25.3073	$25.31	$25.30	$25.30
Purchase #3	$101.32	9.250%	$110.6921	$110.69	$110.70	$110.70
Purchase #4	$81.46	5.408%	$85.8654	$85.87	$85.85	$85.90
Purchase #5	$99.66	9.830%	$109.4566	$109.46	$109.45	$109.50
Purchase #6	$172.62	11.509%	$192.4868	$192.49	$192.50	$192.50
Purchase #7	$235.93	13.845%	$268.5945	$268.59	$268.60	$268.60
7 purchase totals =	$892.46		$988.4160	$988.42	$988.40	$988.50