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	$42.90	11.456%	$47.8146	$47.81	$47.80	$47.80
Purchase #2	$60.82	7.806%	$65.5676	$65.57	$65.55	$65.60
Purchase #3	$200.39	6.761%	$213.9384	$213.94	$213.95	$213.90
Purchase #4	$158.67	12.218%	$178.0563	$178.06	$178.05	$178.10
Purchase #5	$97.42	11.168%	$108.2999	$108.30	$108.30	$108.30
Purchase #6	$54.58	9.280%	$59.645	$59.65	$59.65	$59.60
Purchase #7	$85.45	5.603%	$90.2378	$90.24	$90.25	$90.20
7 purchase totals =	$700.23		$763.5596	$763.57	$763.55	$763.50