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	$244.25	10.707%	$270.4018	$270.40	$270.40	$270.40
Purchase #2	$176.70	11.756%	$197.4729	$197.47	$197.45	$197.50
Purchase #3	$234.45	12.386%	$263.489	$263.49	$263.50	$263.50
Purchase #4	$40.47	12.330%	$45.46	$45.46	$45.45	$45.50
Purchase #5	$108.89	13.430%	$123.5139	$123.51	$123.50	$123.50
Purchase #6	$133.35	13.318%	$151.1096	$151.11	$151.10	$151.10
Purchase #7	$57.81	8.245%	$62.5764	$62.58	$62.60	$62.60
7 purchase totals =	$995.92		$1,114.0236	$1,114.02	$1,114.00	$1,114.10