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	$123.67	7.280%	$132.6732	$132.67	$132.65	$132.70
Purchase #2	$128.99	12.447%	$145.0454	$145.05	$145.05	$145.00
Purchase #3	$68.85	9.731%	$75.5498	$75.55	$75.55	$75.50
Purchase #4	$141.69	6.868%	$151.4213	$151.42	$151.40	$151.40
Purchase #5	$142.60	8.152%	$154.2248	$154.22	$154.20	$154.20
Purchase #6	$86.88	4.166%	$90.4994	$90.50	$90.50	$90.50
Purchase #7	$46.40	12.333%	$52.1225	$52.12	$52.10	$52.10
7 purchase totals =	$739.08		$801.5364	$801.53	$801.45	$801.40