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	$14.76	9.434%	$16.1525	$16.15	$16.15	$16.20
Purchase #2	$42.82	8.852%	$46.6104	$46.61	$46.60	$46.60
Purchase #3	$45.97	13.522%	$52.1861	$52.19	$52.20	$52.20
Purchase #4	$11.97	4.161%	$12.4681	$12.47	$12.45	$12.50
Purchase #5	$26.83	5.257%	$28.2405	$28.24	$28.25	$28.20
Purchase #6	$137.34	7.130%	$147.1323	$147.13	$147.15	$147.10
Purchase #7	$82.87	7.839%	$89.3662	$89.37	$89.35	$89.40
7 purchase totals =	$362.56		$392.1561	$392.16	$392.15	$392.20