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	$159.61	12.873%	$180.1566	$180.16	$180.15	$180.20
Purchase #2	$86.36	11.780%	$96.5332	$96.53	$96.55	$96.50
Purchase #3	$127.52	13.775%	$145.0859	$145.09	$145.10	$145.10
Purchase #4	$132.81	13.641%	$150.9266	$150.93	$150.95	$150.90
Purchase #5	$95.27	13.523%	$108.1534	$108.15	$108.15	$108.20
Purchase #6	$111.70	11.569%	$124.6226	$124.62	$124.60	$124.60
Purchase #7	$243.37	5.339%	$256.3635	$256.36	$256.35	$256.40
7 purchase totals =	$956.64		$1,061.8418	$1,061.84	$1,061.85	$1,061.90