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	$127.31	12.784%	$143.5853	$143.59	$143.60	$143.60
Purchase #2	$246.69	10.189%	$271.8252	$271.83	$271.85	$271.80
Purchase #3	$68.43	10.858%	$75.8601	$75.86	$75.85	$75.90
Purchase #4	$230.52	4.633%	$241.2	$241.20	$241.20	$241.20
Purchase #5	$90.89	12.541%	$102.2885	$102.29	$102.30	$102.30
Purchase #6	$115.75	12.534%	$130.2581	$130.26	$130.25	$130.30
Purchase #7	$37.87	13.504%	$42.984	$42.98	$43.00	$43.00
7 purchase totals =	$917.46		$1,008.0012	$1,008.01	$1,008.05	$1,008.10