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	$34.28	8.737%	$37.275	$37.28	$37.30	$37.30
Purchase #2	$40.45	13.325%	$45.84	$45.84	$45.85	$45.80
Purchase #3	$133.87	11.752%	$149.6024	$149.60	$149.60	$149.60
Purchase #4	$34.45	7.637%	$37.0809	$37.08	$37.10	$37.10
Purchase #5	$218.92	11.676%	$244.4811	$244.48	$244.50	$244.50
Purchase #6	$14.30	11.796%	$15.9868	$15.99	$16.00	$16.00
Purchase #7	$53.43	10.676%	$59.1342	$59.13	$59.15	$59.10
7 purchase totals =	$529.70		$589.4004	$589.40	$589.50	$589.40