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	$65.72	10.757%	$72.7895	$72.79	$72.80	$72.80
Purchase #2	$80.84	7.321%	$86.7583	$86.76	$86.75	$86.80
Purchase #3	$11.27	11.744%	$12.5935	$12.59	$12.60	$12.60
Purchase #4	$12.91	10.577%	$14.2755	$14.28	$14.30	$14.30
Purchase #5	$64.93	10.132%	$71.5087	$71.51	$71.50	$71.50
Purchase #6	$172.59	11.792%	$192.9418	$192.94	$192.95	$192.90
Purchase #7	$62.73	5.366%	$66.0961	$66.10	$66.10	$66.10
7 purchase totals =	$470.99		$516.9634	$516.97	$517.00	$517.00