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	$208.48	4.129%	$217.0881	$217.09	$217.10	$217.10
Purchase #2	$149.32	7.339%	$160.2786	$160.28	$160.30	$160.30
Purchase #3	$217.90	6.569%	$232.2139	$232.21	$232.20	$232.20
Purchase #4	$17.50	4.212%	$18.2371	$18.24	$18.25	$18.20
Purchase #5	$10.80	6.596%	$11.5124	$11.51	$11.50	$11.50
Purchase #6	$240.78	3.370%	$248.8943	$248.89	$248.90	$248.90
Purchase #7	$123.41	3.615%	$127.8713	$127.87	$127.85	$127.90
7 purchase totals =	$968.19		$1,016.0957	$1,016.09	$1,016.10	$1,016.10