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	$39.30	9.531%	$43.0457	$43.05	$43.05	$43.00
Purchase #2	$15.54	10.325%	$17.1445	$17.14	$17.15	$17.10
Purchase #3	$89.42	10.757%	$99.0389	$99.04	$99.05	$99.00
Purchase #4	$241.71	8.221%	$261.581	$261.58	$261.60	$261.60
Purchase #5	$41.78	7.657%	$44.9791	$44.98	$45.00	$45.00
Purchase #6	$208.92	6.393%	$222.2763	$222.28	$222.30	$222.30
Purchase #7	$42.82	8.429%	$46.4293	$46.43	$46.45	$46.40
7 purchase totals =	$679.49		$734.4948	$734.50	$734.60	$734.40