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	$186.42	9.679%	$204.4636	$204.46	$204.45	$204.50
Purchase #2	$113.35	5.498%	$119.582	$119.58	$119.60	$119.60
Purchase #3	$128.76	3.625%	$133.4276	$133.43	$133.45	$133.40
Purchase #4	$172.92	7.261%	$185.4757	$185.48	$185.50	$185.50
Purchase #5	$89.93	11.763%	$100.5085	$100.51	$100.50	$100.50
Purchase #6	$197.67	5.272%	$208.0912	$208.09	$208.10	$208.10
Purchase #7	$39.67	10.491%	$43.8318	$43.83	$43.85	$43.80
7 purchase totals =	$928.72		$995.3804	$995.38	$995.45	$995.40