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	$78.86	8.549%	$85.6017	$85.60	$85.60	$85.60
Purchase #2	$102.53	13.746%	$116.6238	$116.62	$116.60	$116.60
Purchase #3	$81.43	6.577%	$86.7857	$86.79	$86.80	$86.80
Purchase #4	$209.56	5.396%	$220.8679	$220.87	$220.85	$220.90
Purchase #5	$191.50	10.324%	$211.2705	$211.27	$211.25	$211.30
Purchase #6	$231.69	12.750%	$261.2305	$261.23	$261.25	$261.20
Purchase #7	$105.58	11.756%	$117.992	$117.99	$118.00	$118.00
7 purchase totals =	$1,001.15		$1,100.3721	$1,100.37	$1,100.35	$1,100.40