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	$23.86	4.325%	$24.8919	$24.89	$24.90	$24.90
Purchase #2	$177.81	5.807%	$188.1354	$188.14	$188.15	$188.10
Purchase #3	$105.71	3.525%	$109.4363	$109.44	$109.45	$109.40
Purchase #4	$184.90	4.857%	$193.8806	$193.88	$193.90	$193.90
Purchase #5	$233.91	9.308%	$255.6823	$255.68	$255.70	$255.70
Purchase #6	$58.49	5.382%	$61.6379	$61.64	$61.65	$61.60
Purchase #7	$238.29	13.462%	$270.3686	$270.37	$270.35	$270.40
7 purchase totals =	$1,022.97		$1,104.0330	$1,104.04	$1,104.10	$1,104.00