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	$160.84	4.587%	$168.2177	$168.22	$168.20	$168.20
Purchase #2	$100.77	7.756%	$108.5857	$108.59	$108.60	$108.60
Purchase #3	$87.89	8.404%	$95.2763	$95.28	$95.30	$95.30
Purchase #4	$187.32	10.815%	$207.5787	$207.58	$207.60	$207.60
Purchase #5	$169.32	10.807%	$187.6184	$187.62	$187.60	$187.60
Purchase #6	$17.86	5.642%	$18.8677	$18.87	$18.85	$18.90
Purchase #7	$205.28	8.475%	$222.6775	$222.68	$222.70	$222.70
7 purchase totals =	$929.28		$1,008.8220	$1,008.84	$1,008.85	$1,008.90