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	$153.45	12.691%	$172.9243	$172.92	$172.90	$172.90
Purchase #2	$166.94	7.768%	$179.9079	$179.91	$179.90	$179.90
Purchase #3	$184.69	13.152%	$208.9804	$208.98	$209.00	$209.00
Purchase #4	$101.77	13.819%	$115.8336	$115.83	$115.85	$115.80
Purchase #5	$19.78	13.604%	$22.4709	$22.47	$22.45	$22.50
Purchase #6	$92.75	5.226%	$97.5971	$97.60	$97.60	$97.60
Purchase #7	$234.72	7.176%	$251.5635	$251.56	$251.55	$251.60
7 purchase totals =	$954.10		$1,049.2777	$1,049.27	$1,049.25	$1,049.30