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	$146.66	8.163%	$158.6319	$158.63	$158.65	$158.60
Purchase #2	$111.42	6.660%	$118.8406	$118.84	$118.85	$118.80
Purchase #3	$178.63	12.850%	$201.584	$201.58	$201.60	$201.60
Purchase #4	$118.26	4.242%	$123.2766	$123.28	$123.30	$123.30
Purchase #5	$34.83	10.793%	$38.5892	$38.59	$38.60	$38.60
Purchase #6	$212.89	7.795%	$229.4848	$229.48	$229.50	$229.50
Purchase #7	$161.31	8.178%	$174.5019	$174.50	$174.50	$174.50
7 purchase totals =	$964.00		$1,044.9090	$1,044.90	$1,045.00	$1,044.90