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	$101.92	7.582%	$109.6476	$109.65	$109.65	$109.60
Purchase #2	$51.87	6.841%	$55.4184	$55.42	$55.40	$55.40
Purchase #3	$127.76	13.652%	$145.2018	$145.20	$145.20	$145.20
Purchase #4	$113.34	9.291%	$123.8704	$123.87	$123.85	$123.90
Purchase #5	$133.78	4.302%	$139.5352	$139.54	$139.55	$139.50
Purchase #6	$245.55	5.309%	$258.5862	$258.59	$258.60	$258.60
Purchase #7	$116.30	3.683%	$120.5833	$120.58	$120.60	$120.60
7 purchase totals =	$890.52		$952.8429	$952.85	$952.85	$952.80