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	$75.32	9.200%	$82.2494	$82.25	$82.25	$82.20
Purchase #2	$136.29	10.862%	$151.0938	$151.09	$151.10	$151.10
Purchase #3	$9.93	5.736%	$10.4996	$10.50	$10.50	$10.50
Purchase #4	$12.54	4.873%	$13.1511	$13.15	$13.15	$13.20
Purchase #5	$110.40	10.134%	$121.5879	$121.59	$121.60	$121.60
Purchase #6	$128.82	9.869%	$141.5332	$141.53	$141.55	$141.50
Purchase #7	$45.26	4.689%	$47.3822	$47.38	$47.40	$47.40
7 purchase totals =	$518.56		$567.4972	$567.49	$567.55	$567.50