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	$192.98	3.751%	$200.2187	$200.22	$200.20	$200.20
Purchase #2	$211.26	11.202%	$234.9253	$234.93	$234.95	$234.90
Purchase #3	$112.70	13.126%	$127.493	$127.49	$127.50	$127.50
Purchase #4	$145.88	4.866%	$152.9785	$152.98	$153.00	$153.00
Purchase #5	$172.85	9.388%	$189.0772	$189.08	$189.10	$189.10
Purchase #6	$56.42	12.392%	$63.4116	$63.41	$63.40	$63.40
Purchase #7	$140.35	10.554%	$155.1625	$155.16	$155.15	$155.20
7 purchase totals =	$1,032.44		$1,123.2668	$1,123.27	$1,123.30	$1,123.30