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	$118.78	10.163%	$130.8516	$130.85	$130.85	$130.90
Purchase #2	$74.69	9.277%	$81.619	$81.62	$81.60	$81.60
Purchase #3	$161.26	11.651%	$180.0484	$180.05	$180.05	$180.00
Purchase #4	$38.83	4.564%	$40.6022	$40.60	$40.60	$40.60
Purchase #5	$90.51	11.523%	$100.9395	$100.94	$100.95	$100.90
Purchase #6	$235.75	11.340%	$262.4841	$262.48	$262.50	$262.50
Purchase #7	$56.40	10.670%	$62.4179	$62.42	$62.40	$62.40
7 purchase totals =	$776.22		$858.9627	$858.96	$858.95	$858.90