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	$67.85	3.262%	$70.0633	$70.06	$70.05	$70.10
Purchase #2	$48.61	4.141%	$50.6229	$50.62	$50.60	$50.60
Purchase #3	$225.59	11.571%	$251.693	$251.69	$251.70	$251.70
Purchase #4	$64.26	12.105%	$72.0387	$72.04	$72.05	$72.00
Purchase #5	$173.59	9.759%	$190.5306	$190.53	$190.55	$190.50
Purchase #6	$210.89	11.266%	$234.6489	$234.65	$234.65	$234.60
Purchase #7	$178.71	11.182%	$198.6934	$198.69	$198.70	$198.70
7 purchase totals =	$969.50		$1,068.2908	$1,068.28	$1,068.30	$1,068.20