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	$141.79	11.761%	$158.4659	$158.47	$158.45	$158.50
Purchase #2	$212.56	8.699%	$231.0506	$231.05	$231.05	$231.10
Purchase #3	$102.47	13.472%	$116.2748	$116.27	$116.25	$116.30
Purchase #4	$124.42	5.771%	$131.6003	$131.60	$131.60	$131.60
Purchase #5	$87.56	13.468%	$99.3526	$99.35	$99.35	$99.40
Purchase #6	$128.74	11.812%	$143.9468	$143.95	$143.95	$143.90
Purchase #7	$218.79	4.756%	$229.1957	$229.20	$229.20	$229.20
7 purchase totals =	$1,016.33		$1,109.8867	$1,109.89	$1,109.85	$1,110.00