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	$108.45	13.443%	$123.0289	$123.03	$123.05	$123.00
Purchase #2	$31.81	5.587%	$33.5872	$33.59	$33.60	$33.60
Purchase #3	$62.29	7.286%	$66.8284	$66.83	$66.85	$66.80
Purchase #4	$233.55	3.686%	$242.1587	$242.16	$242.15	$242.20
Purchase #5	$232.91	7.681%	$250.7998	$250.80	$250.80	$250.80
Purchase #6	$111.93	11.523%	$124.8277	$124.83	$124.85	$124.80
Purchase #7	$226.71	11.632%	$253.0809	$253.08	$253.10	$253.10
7 purchase totals =	$1,007.65		$1,094.3116	$1,094.32	$1,094.40	$1,094.30