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	$233.74	8.870%	$254.4727	$254.47	$254.45	$254.50
Purchase #2	$216.39	7.107%	$231.7688	$231.77	$231.75	$231.80
Purchase #3	$123.26	13.407%	$139.7855	$139.79	$139.80	$139.80
Purchase #4	$83.45	8.554%	$90.5883	$90.59	$90.60	$90.60
Purchase #5	$15.50	5.588%	$16.3661	$16.37	$16.35	$16.40
Purchase #6	$227.83	10.366%	$251.4469	$251.45	$251.45	$251.40
Purchase #7	$27.86	3.464%	$28.8251	$28.83	$28.85	$28.80
7 purchase totals =	$928.03		$1,013.2534	$1,013.27	$1,013.25	$1,013.30