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	$170.73	6.710%	$182.186	$182.19	$182.20	$182.20
Purchase #2	$92.77	9.569%	$101.6472	$101.65	$101.65	$101.60
Purchase #3	$198.43	11.622%	$221.4915	$221.49	$221.50	$221.50
Purchase #4	$99.83	11.686%	$111.4961	$111.50	$111.50	$111.50
Purchase #5	$56.36	12.155%	$63.2106	$63.21	$63.20	$63.20
Purchase #6	$111.39	10.803%	$123.4235	$123.42	$123.40	$123.40
Purchase #7	$143.80	10.578%	$159.0112	$159.01	$159.00	$159.00
7 purchase totals =	$873.31		$962.4661	$962.47	$962.45	$962.40