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	$113.73	8.523%	$123.4232	$123.42	$123.40	$123.40
Purchase #2	$147.95	7.251%	$158.6779	$158.68	$158.70	$158.70
Purchase #3	$140.50	3.296%	$145.1309	$145.13	$145.15	$145.10
Purchase #4	$168.94	10.786%	$187.1619	$187.16	$187.15	$187.20
Purchase #5	$38.98	3.447%	$40.3236	$40.32	$40.30	$40.30
Purchase #6	$158.41	8.869%	$172.4594	$172.46	$172.45	$172.50
Purchase #7	$206.41	13.409%	$234.0875	$234.09	$234.10	$234.10
7 purchase totals =	$974.92		$1,061.2644	$1,061.26	$1,061.25	$1,061.30