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	$140.97	10.775%	$156.1595	$156.16	$156.15	$156.20
Purchase #2	$156.37	11.163%	$173.8256	$173.83	$173.85	$173.80
Purchase #3	$42.38	8.117%	$45.82	$45.82	$45.80	$45.80
Purchase #4	$138.83	7.665%	$149.4713	$149.47	$149.45	$149.50
Purchase #5	$222.90	8.513%	$241.8755	$241.88	$241.90	$241.90
Purchase #6	$198.43	6.398%	$211.1256	$211.13	$211.15	$211.10
Purchase #7	$196.92	8.745%	$214.1407	$214.14	$214.15	$214.10
7 purchase totals =	$1,096.80		$1,192.4182	$1,192.43	$1,192.45	$1,192.40