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	$132.79	9.597%	$145.5339	$145.53	$145.55	$145.50
Purchase #2	$31.93	7.311%	$34.2644	$34.26	$34.25	$34.30
Purchase #3	$126.32	4.438%	$131.9261	$131.93	$131.95	$131.90
Purchase #4	$166.93	9.109%	$182.1357	$182.14	$182.15	$182.10
Purchase #5	$60.63	8.113%	$65.5489	$65.55	$65.55	$65.50
Purchase #6	$185.51	7.845%	$200.0633	$200.06	$200.05	$200.10
Purchase #7	$234.81	5.659%	$248.0979	$248.10	$248.10	$248.10
7 purchase totals =	$938.92		$1,007.5702	$1,007.57	$1,007.60	$1,007.50