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	$208.46	9.451%	$228.1616	$228.16	$228.15	$228.20
Purchase #2	$71.71	6.451%	$76.336	$76.34	$76.35	$76.30
Purchase #3	$95.51	5.218%	$100.4937	$100.49	$100.50	$100.50
Purchase #4	$167.56	10.157%	$184.5791	$184.58	$184.60	$184.60
Purchase #5	$64.59	8.221%	$69.8999	$69.90	$69.90	$69.90
Purchase #6	$127.65	9.528%	$139.8125	$139.81	$139.80	$139.80
Purchase #7	$197.52	9.342%	$215.9723	$215.97	$215.95	$216.00
7 purchase totals =	$933.00		$1,015.2551	$1,015.25	$1,015.25	$1,015.30