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	$75.86	10.629%	$83.9232	$83.92	$83.90	$83.90
Purchase #2	$191.84	6.814%	$204.912	$204.91	$204.90	$204.90
Purchase #3	$238.29	8.328%	$258.1348	$258.13	$258.15	$258.10
Purchase #4	$129.55	12.261%	$145.4341	$145.43	$145.45	$145.40
Purchase #5	$105.74	11.153%	$117.5332	$117.53	$117.55	$117.50
Purchase #6	$192.32	6.870%	$205.5324	$205.53	$205.55	$205.50
Purchase #7	$137.89	4.349%	$143.8868	$143.89	$143.90	$143.90
7 purchase totals =	$1,071.49		$1,159.3565	$1,159.34	$1,159.40	$1,159.20