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	$207.70	9.688%	$227.822	$227.82	$227.80	$227.80
Purchase #2	$151.71	4.489%	$158.5203	$158.52	$158.50	$158.50
Purchase #3	$59.77	4.442%	$62.425	$62.43	$62.45	$62.40
Purchase #4	$140.59	4.408%	$146.7872	$146.79	$146.80	$146.80
Purchase #5	$154.60	10.791%	$171.2829	$171.28	$171.30	$171.30
Purchase #6	$113.54	4.387%	$118.521	$118.52	$118.50	$118.50
Purchase #7	$57.62	13.868%	$65.6107	$65.61	$65.60	$65.60
7 purchase totals =	$885.53		$950.9691	$950.97	$950.95	$950.90