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	$108.80	13.781%	$123.7937	$123.79	$123.80	$123.80
Purchase #2	$127.29	9.798%	$139.7619	$139.76	$139.75	$139.80
Purchase #3	$172.98	13.735%	$196.7388	$196.74	$196.75	$196.70
Purchase #4	$168.87	11.213%	$187.8054	$187.81	$187.80	$187.80
Purchase #5	$133.66	11.245%	$148.6901	$148.69	$148.70	$148.70
Purchase #6	$106.30	10.621%	$117.5901	$117.59	$117.60	$117.60
Purchase #7	$146.72	13.395%	$166.3731	$166.37	$166.35	$166.40
7 purchase totals =	$964.62		$1,080.7531	$1,080.75	$1,080.75	$1,080.80