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	$175.29	5.450%	$184.8433	$184.84	$184.85	$184.80
Purchase #2	$177.65	12.793%	$200.3768	$200.38	$200.40	$200.40
Purchase #3	$42.29	6.429%	$45.0088	$45.01	$45.00	$45.00
Purchase #4	$24.78	13.670%	$28.1674	$28.17	$28.15	$28.20
Purchase #5	$48.45	11.724%	$54.1303	$54.13	$54.15	$54.10
Purchase #6	$232.76	9.691%	$255.3168	$255.32	$255.30	$255.30
Purchase #7	$126.51	5.493%	$133.4592	$133.46	$133.45	$133.50
7 purchase totals =	$827.73		$901.3026	$901.31	$901.30	$901.30