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	$126.63	9.636%	$138.8321	$138.83	$138.85	$138.80
Purchase #2	$65.92	10.441%	$72.8027	$72.80	$72.80	$72.80
Purchase #3	$51.45	11.360%	$57.2947	$57.29	$57.30	$57.30
Purchase #4	$96.44	12.301%	$108.3031	$108.30	$108.30	$108.30
Purchase #5	$13.78	13.697%	$15.6674	$15.67	$15.65	$15.70
Purchase #6	$101.31	10.149%	$111.592	$111.59	$111.60	$111.60
Purchase #7	$112.58	9.814%	$123.6286	$123.63	$123.65	$123.60
7 purchase totals =	$568.11		$628.1206	$628.11	$628.15	$628.10