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	$115.99	9.393%	$126.8849	$126.88	$126.90	$126.90
Purchase #2	$72.82	7.616%	$78.366	$78.37	$78.35	$78.40
Purchase #3	$81.29	10.302%	$89.6645	$89.66	$89.65	$89.70
Purchase #4	$72.72	12.132%	$81.5424	$81.54	$81.55	$81.50
Purchase #5	$93.52	13.448%	$106.0966	$106.10	$106.10	$106.10
Purchase #6	$176.62	6.230%	$187.6234	$187.62	$187.60	$187.60
Purchase #7	$48.43	8.829%	$52.7059	$52.71	$52.70	$52.70
7 purchase totals =	$661.39		$722.8837	$722.88	$722.85	$722.90