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	$180.51	9.744%	$198.0989	$198.10	$198.10	$198.10
Purchase #2	$10.96	12.487%	$12.3286	$12.33	$12.35	$12.30
Purchase #3	$40.63	3.122%	$41.8985	$41.90	$41.90	$41.90
Purchase #4	$117.94	11.751%	$131.7991	$131.80	$131.80	$131.80
Purchase #5	$88.83	4.145%	$92.512	$92.51	$92.50	$92.50
Purchase #6	$172.99	4.150%	$180.1691	$180.17	$180.15	$180.20
Purchase #7	$204.83	4.509%	$214.0658	$214.07	$214.05	$214.10
7 purchase totals =	$816.69		$870.8720	$870.88	$870.85	$870.90