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	$244.56	10.342%	$269.8524	$269.85	$269.85	$269.90
Purchase #2	$54.31	13.591%	$61.6913	$61.69	$61.70	$61.70
Purchase #3	$93.65	10.274%	$103.2716	$103.27	$103.25	$103.30
Purchase #4	$46.37	11.669%	$51.7809	$51.78	$51.80	$51.80
Purchase #5	$204.54	11.301%	$227.6551	$227.66	$227.65	$227.70
Purchase #6	$155.46	7.159%	$166.5894	$166.59	$166.60	$166.60
Purchase #7	$70.93	5.729%	$74.9936	$74.99	$75.00	$75.00
7 purchase totals =	$869.82		$955.8343	$955.83	$955.85	$956.00