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	$112.39	3.352%	$116.1573	$116.16	$116.15	$116.20
Purchase #2	$233.72	3.371%	$241.5987	$241.60	$241.60	$241.60
Purchase #3	$50.42	10.304%	$55.6153	$55.62	$55.60	$55.60
Purchase #4	$236.51	10.573%	$261.5162	$261.52	$261.50	$261.50
Purchase #5	$127.89	8.649%	$138.9512	$138.95	$138.95	$139.00
Purchase #6	$34.91	11.450%	$38.9072	$38.91	$38.90	$38.90
Purchase #7	$172.39	13.264%	$195.2558	$195.26	$195.25	$195.30
7 purchase totals =	$968.23		$1,048.0017	$1,048.02	$1,047.95	$1,048.10