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	$43.27	12.329%	$48.6048	$48.60	$48.60	$48.60
Purchase #2	$163.71	9.112%	$178.6273	$178.63	$178.65	$178.60
Purchase #3	$123.43	13.335%	$139.8894	$139.89	$139.90	$139.90
Purchase #4	$159.42	12.548%	$179.424	$179.42	$179.40	$179.40
Purchase #5	$52.86	4.244%	$55.1034	$55.10	$55.10	$55.10
Purchase #6	$200.79	6.856%	$214.5562	$214.56	$214.55	$214.60
Purchase #7	$212.29	7.778%	$228.8019	$228.80	$228.80	$228.80
7 purchase totals =	$955.77		$1,045.0070	$1,045.00	$1,045.00	$1,045.00