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	$158.62	3.677%	$164.4525	$164.45	$164.45	$164.50
Purchase #2	$42.60	8.792%	$46.3454	$46.35	$46.35	$46.30
Purchase #3	$196.35	12.597%	$221.0842	$221.08	$221.10	$221.10
Purchase #4	$72.67	12.451%	$81.7181	$81.72	$81.70	$81.70
Purchase #5	$185.33	4.340%	$193.3733	$193.37	$193.35	$193.40
Purchase #6	$178.81	6.304%	$190.0822	$190.08	$190.10	$190.10
Purchase #7	$151.51	13.309%	$171.6745	$171.67	$171.65	$171.70
7 purchase totals =	$985.89		$1,068.7302	$1,068.72	$1,068.70	$1,068.80