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	$233.51	8.130%	$252.4944	$252.49	$252.50	$252.50
Purchase #2	$74.76	3.633%	$77.476	$77.48	$77.50	$77.50
Purchase #3	$173.96	10.595%	$192.3911	$192.39	$192.40	$192.40
Purchase #4	$70.97	10.438%	$78.3778	$78.38	$78.40	$78.40
Purchase #5	$146.29	6.643%	$156.008	$156.01	$156.00	$156.00
Purchase #6	$246.90	6.169%	$262.1313	$262.13	$262.15	$262.10
Purchase #7	$64.65	10.152%	$71.2133	$71.21	$71.20	$71.20
7 purchase totals =	$1,011.04		$1,090.0919	$1,090.09	$1,090.15	$1,090.10