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	$152.63	6.341%	$162.3083	$162.31	$162.30	$162.30
Purchase #2	$227.82	4.556%	$238.1995	$238.20	$238.20	$238.20
Purchase #3	$124.59	13.397%	$141.2813	$141.28	$141.30	$141.30
Purchase #4	$146.38	12.278%	$164.3525	$164.35	$164.35	$164.40
Purchase #5	$11.92	5.748%	$12.6052	$12.61	$12.60	$12.60
Purchase #6	$74.52	10.537%	$82.3722	$82.37	$82.35	$82.40
Purchase #7	$164.72	7.407%	$176.9208	$176.92	$176.90	$176.90
7 purchase totals =	$902.58		$978.0398	$978.04	$978.00	$978.10