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	$64.28	3.549%	$66.5613	$66.56	$66.55	$66.60
Purchase #2	$101.90	10.519%	$112.6189	$112.62	$112.60	$112.60
Purchase #3	$70.35	3.617%	$72.8946	$72.89	$72.90	$72.90
Purchase #4	$14.52	9.768%	$15.9383	$15.94	$15.95	$15.90
Purchase #5	$55.44	9.710%	$60.8232	$60.82	$60.80	$60.80
Purchase #6	$211.28	10.519%	$233.5045	$233.50	$233.50	$233.50
Purchase #7	$64.70	12.787%	$72.9732	$72.97	$72.95	$73.00
7 purchase totals =	$582.47		$635.3140	$635.30	$635.25	$635.30