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	$207.92	9.618%	$227.9177	$227.92	$227.90	$227.90
Purchase #2	$177.26	7.262%	$190.1326	$190.13	$190.15	$190.10
Purchase #3	$60.25	8.851%	$65.5827	$65.58	$65.60	$65.60
Purchase #4	$211.83	12.286%	$237.8554	$237.86	$237.85	$237.90
Purchase #5	$163.64	13.393%	$185.5563	$185.56	$185.55	$185.60
Purchase #6	$76.40	5.787%	$80.8213	$80.82	$80.80	$80.80
Purchase #7	$81.62	10.127%	$89.8857	$89.89	$89.90	$89.90
7 purchase totals =	$978.92		$1,077.7517	$1,077.76	$1,077.75	$1,077.80