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	$66.43	8.625%	$72.1596	$72.16	$72.15	$72.20
Purchase #2	$32.25	7.176%	$34.5643	$34.56	$34.55	$34.60
Purchase #3	$214.41	11.276%	$238.5869	$238.59	$238.60	$238.60
Purchase #4	$141.57	3.517%	$146.549	$146.55	$146.55	$146.50
Purchase #5	$206.57	5.509%	$217.9499	$217.95	$217.95	$217.90
Purchase #6	$123.33	10.616%	$136.4227	$136.42	$136.40	$136.40
Purchase #7	$85.31	4.386%	$89.0517	$89.05	$89.05	$89.10
7 purchase totals =	$869.87		$935.2841	$935.28	$935.25	$935.30