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	$91.51	9.623%	$100.316	$100.32	$100.30	$100.30
Purchase #2	$19.34	12.832%	$21.8217	$21.82	$21.80	$21.80
Purchase #3	$190.93	12.724%	$215.2239	$215.22	$215.20	$215.20
Purchase #4	$13.28	11.861%	$14.8551	$14.86	$14.85	$14.90
Purchase #5	$233.66	12.589%	$263.0755	$263.08	$263.10	$263.10
Purchase #6	$228.59	10.186%	$251.8742	$251.87	$251.85	$251.90
Purchase #7	$238.43	4.616%	$249.4359	$249.44	$249.45	$249.40
7 purchase totals =	$1,015.74		$1,116.6023	$1,116.61	$1,116.55	$1,116.60