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	$143.82	4.614%	$150.4559	$150.46	$150.45	$150.50
Purchase #2	$140.70	12.465%	$158.2383	$158.24	$158.25	$158.20
Purchase #3	$237.81	4.847%	$249.3367	$249.34	$249.35	$249.30
Purchase #4	$75.67	4.247%	$78.8837	$78.88	$78.90	$78.90
Purchase #5	$115.78	9.226%	$126.4619	$126.46	$126.45	$126.50
Purchase #6	$48.88	8.553%	$53.0607	$53.06	$53.05	$53.10
Purchase #7	$205.99	4.310%	$214.8682	$214.87	$214.85	$214.90
7 purchase totals =	$968.65		$1,031.3054	$1,031.31	$1,031.30	$1,031.40