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	$30.95	8.401%	$33.5501	$33.55	$33.55	$33.60
Purchase #2	$16.45	3.770%	$17.0702	$17.07	$17.05	$17.10
Purchase #3	$160.90	9.833%	$176.7213	$176.72	$176.70	$176.70
Purchase #4	$81.81	10.863%	$90.697	$90.70	$90.70	$90.70
Purchase #5	$147.69	11.414%	$164.5473	$164.55	$164.55	$164.50
Purchase #6	$98.82	8.760%	$107.4766	$107.48	$107.50	$107.50
Purchase #7	$100.48	8.793%	$109.3152	$109.32	$109.30	$109.30
7 purchase totals =	$637.10		$699.3777	$699.39	$699.35	$699.40