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	$64.45	5.232%	$67.822	$67.82	$67.80	$67.80
Purchase #2	$237.64	10.625%	$262.8893	$262.89	$262.90	$262.90
Purchase #3	$160.96	9.439%	$176.153	$176.15	$176.15	$176.20
Purchase #4	$39.78	7.755%	$42.8649	$42.86	$42.85	$42.90
Purchase #5	$148.97	6.200%	$158.2061	$158.21	$158.20	$158.20
Purchase #6	$92.83	5.716%	$98.1362	$98.14	$98.15	$98.10
Purchase #7	$195.87	6.301%	$208.2118	$208.21	$208.20	$208.20
7 purchase totals =	$940.50		$1,014.2833	$1,014.28	$1,014.25	$1,014.30