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	$239.38	13.466%	$271.6149	$271.61	$271.60	$271.60
Purchase #2	$9.30	10.295%	$10.2574	$10.26	$10.25	$10.30
Purchase #3	$157.93	8.423%	$171.2324	$171.23	$171.25	$171.20
Purchase #4	$231.64	12.734%	$261.137	$261.14	$261.15	$261.10
Purchase #5	$143.91	5.800%	$152.2568	$152.26	$152.25	$152.30
Purchase #6	$121.67	7.384%	$130.6541	$130.65	$130.65	$130.70
Purchase #7	$78.64	8.476%	$85.3055	$85.31	$85.30	$85.30
7 purchase totals =	$982.47		$1,082.4581	$1,082.46	$1,082.45	$1,082.50