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	$245.83	10.752%	$272.2616	$272.26	$272.25	$272.30
Purchase #2	$224.36	4.131%	$233.6283	$233.63	$233.65	$233.60
Purchase #3	$27.42	7.412%	$29.4524	$29.45	$29.45	$29.50
Purchase #4	$144.42	7.559%	$155.3367	$155.34	$155.35	$155.30
Purchase #5	$249.30	9.304%	$272.4949	$272.49	$272.50	$272.50
Purchase #6	$128.32	10.777%	$142.149	$142.15	$142.15	$142.10
Purchase #7	$51.88	9.548%	$56.8335	$56.83	$56.85	$56.80
7 purchase totals =	$1,071.53		$1,162.1564	$1,162.15	$1,162.20	$1,162.10