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	$136.59	10.158%	$150.4648	$150.46	$150.45	$150.50
Purchase #2	$80.28	9.448%	$87.8649	$87.86	$87.85	$87.90
Purchase #3	$114.95	13.397%	$130.3499	$130.35	$130.35	$130.30
Purchase #4	$144.56	9.831%	$158.7717	$158.77	$158.75	$158.80
Purchase #5	$157.41	9.712%	$172.6977	$172.70	$172.70	$172.70
Purchase #6	$165.27	5.365%	$174.1367	$174.14	$174.15	$174.10
Purchase #7	$189.86	11.580%	$211.8458	$211.85	$211.85	$211.80
7 purchase totals =	$988.92		$1,086.1315	$1,086.13	$1,086.10	$1,086.10