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	$167.61	13.566%	$190.348	$190.35	$190.35	$190.30
Purchase #2	$134.58	12.391%	$151.2558	$151.26	$151.25	$151.30
Purchase #3	$36.72	9.157%	$40.0825	$40.08	$40.10	$40.10
Purchase #4	$183.61	3.491%	$190.0198	$190.02	$190.00	$190.00
Purchase #5	$222.62	7.157%	$238.5529	$238.55	$238.55	$238.60
Purchase #6	$38.96	13.208%	$44.1058	$44.11	$44.10	$44.10
Purchase #7	$163.33	7.569%	$175.6924	$175.69	$175.70	$175.70
7 purchase totals =	$947.43		$1,030.0572	$1,030.06	$1,030.05	$1,030.10