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	$164.51	10.724%	$182.1521	$182.15	$182.15	$182.20
Purchase #2	$92.76	8.457%	$100.6047	$100.60	$100.60	$100.60
Purchase #3	$231.67	11.457%	$258.2124	$258.21	$258.20	$258.20
Purchase #4	$123.40	13.813%	$140.4452	$140.45	$140.45	$140.40
Purchase #5	$67.97	5.853%	$71.9483	$71.95	$71.95	$71.90
Purchase #6	$75.82	6.161%	$80.4913	$80.49	$80.50	$80.50
Purchase #7	$56.72	6.283%	$60.2837	$60.28	$60.30	$60.30
7 purchase totals =	$812.85		$894.1377	$894.13	$894.15	$894.10