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	$131.66	9.419%	$144.0611	$144.06	$144.05	$144.10
Purchase #2	$174.89	8.394%	$189.5703	$189.57	$189.55	$189.60
Purchase #3	$95.65	10.405%	$105.6024	$105.60	$105.60	$105.60
Purchase #4	$81.32	10.327%	$89.7179	$89.72	$89.70	$89.70
Purchase #5	$29.73	5.252%	$31.2914	$31.29	$31.30	$31.30
Purchase #6	$246.61	13.674%	$280.3315	$280.33	$280.35	$280.30
Purchase #7	$121.80	10.485%	$134.5707	$134.57	$134.55	$134.60
7 purchase totals =	$881.66		$975.1453	$975.14	$975.10	$975.20