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	$10.47	7.855%	$11.2924	$11.29	$11.30	$11.30
Purchase #2	$112.60	3.447%	$116.4813	$116.48	$116.50	$116.50
Purchase #3	$39.37	3.684%	$40.8204	$40.82	$40.80	$40.80
Purchase #4	$12.91	7.317%	$13.8546	$13.85	$13.85	$13.90
Purchase #5	$190.59	12.543%	$214.4957	$214.50	$214.50	$214.50
Purchase #6	$31.80	8.628%	$34.5437	$34.54	$34.55	$34.50
Purchase #7	$15.83	3.444%	$16.3752	$16.38	$16.40	$16.40
7 purchase totals =	$413.57		$447.8633	$447.86	$447.90	$447.90