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	$203.51	5.615%	$214.9371	$214.94	$214.95	$214.90
Purchase #2	$20.43	13.645%	$23.2177	$23.22	$23.20	$23.20
Purchase #3	$143.52	9.269%	$156.8229	$156.82	$156.80	$156.80
Purchase #4	$169.38	12.550%	$190.6372	$190.64	$190.65	$190.60
Purchase #5	$143.59	4.545%	$150.1162	$150.12	$150.10	$150.10
Purchase #6	$100.97	3.596%	$104.6009	$104.60	$104.60	$104.60
Purchase #7	$161.42	12.671%	$181.8735	$181.87	$181.85	$181.90
7 purchase totals =	$942.82		$1,022.2055	$1,022.21	$1,022.15	$1,022.10