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	$205.80	12.650%	$231.8337	$231.83	$231.85	$231.80
Purchase #2	$105.65	10.616%	$116.8658	$116.87	$116.85	$116.90
Purchase #3	$225.38	13.440%	$255.6711	$255.67	$255.65	$255.70
Purchase #4	$38.66	12.784%	$43.6023	$43.60	$43.60	$43.60
Purchase #5	$222.59	12.518%	$250.4538	$250.45	$250.45	$250.50
Purchase #6	$143.71	4.402%	$150.0361	$150.04	$150.05	$150.00
Purchase #7	$132.47	12.209%	$148.6433	$148.64	$148.65	$148.60
7 purchase totals =	$1,074.26		$1,197.1061	$1,197.10	$1,197.10	$1,197.10