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	$156.70	10.156%	$172.6145	$172.61	$172.60	$172.60
Purchase #2	$15.42	7.667%	$16.6023	$16.60	$16.60	$16.60
Purchase #3	$24.86	8.707%	$27.0246	$27.02	$27.00	$27.00
Purchase #4	$20.62	8.173%	$22.3053	$22.31	$22.30	$22.30
Purchase #5	$41.35	5.425%	$43.5932	$43.59	$43.60	$43.60
Purchase #6	$28.66	11.126%	$31.8487	$31.85	$31.85	$31.80
Purchase #7	$45.72	3.219%	$47.1917	$47.19	$47.20	$47.20
7 purchase totals =	$333.33		$361.1803	$361.17	$361.15	$361.10