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	$47.39	12.348%	$53.2417	$53.24	$53.25	$53.20
Purchase #2	$77.28	10.292%	$85.2337	$85.23	$85.25	$85.20
Purchase #3	$230.26	10.709%	$254.9185	$254.92	$254.90	$254.90
Purchase #4	$36.45	11.141%	$40.5109	$40.51	$40.50	$40.50
Purchase #5	$161.93	10.844%	$179.4897	$179.49	$179.50	$179.50
Purchase #6	$146.63	9.517%	$160.5848	$160.58	$160.60	$160.60
Purchase #7	$113.90	11.489%	$126.986	$126.99	$127.00	$127.00
7 purchase totals =	$813.84		$900.9653	$900.96	$901.00	$900.90