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	$145.68	12.620%	$164.0648	$164.06	$164.05	$164.10
Purchase #2	$250.71	4.772%	$262.6739	$262.67	$262.65	$262.70
Purchase #3	$223.86	12.589%	$252.0417	$252.04	$252.05	$252.00
Purchase #4	$53.88	10.476%	$59.5245	$59.52	$59.50	$59.50
Purchase #5	$195.51	11.801%	$218.5821	$218.58	$218.60	$218.60
Purchase #6	$91.74	12.128%	$102.8662	$102.87	$102.85	$102.90
Purchase #7	$57.62	10.190%	$63.4915	$63.49	$63.50	$63.50
7 purchase totals =	$1,019.00		$1,123.2447	$1,123.23	$1,123.20	$1,123.30