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	$70.87	9.163%	$77.3638	$77.36	$77.35	$77.40
Purchase #2	$187.62	12.712%	$211.4703	$211.47	$211.45	$211.50
Purchase #3	$116.61	10.213%	$128.5194	$128.52	$128.50	$128.50
Purchase #4	$190.76	8.210%	$206.4214	$206.42	$206.40	$206.40
Purchase #5	$105.75	13.336%	$119.8528	$119.85	$119.85	$119.90
Purchase #6	$209.80	4.695%	$219.6501	$219.65	$219.65	$219.70
Purchase #7	$141.67	4.665%	$148.2789	$148.28	$148.30	$148.30
7 purchase totals =	$1,023.08		$1,111.5567	$1,111.55	$1,111.50	$1,111.70