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	$54.45	9.493%	$59.6189	$59.62	$59.60	$59.60
Purchase #2	$142.45	3.442%	$147.3531	$147.35	$147.35	$147.40
Purchase #3	$163.89	10.144%	$180.515	$180.52	$180.50	$180.50
Purchase #4	$122.35	11.627%	$136.5756	$136.58	$136.60	$136.60
Purchase #5	$66.31	4.590%	$69.3536	$69.35	$69.35	$69.40
Purchase #6	$66.83	10.592%	$73.9086	$73.91	$73.90	$73.90
Purchase #7	$46.38	5.153%	$48.77	$48.77	$48.75	$48.80
7 purchase totals =	$662.66		$716.0948	$716.10	$716.05	$716.20