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	$35.27	9.417%	$38.5914	$38.59	$38.60	$38.60
Purchase #2	$87.39	13.689%	$99.3528	$99.35	$99.35	$99.40
Purchase #3	$75.33	12.430%	$84.6935	$84.69	$84.70	$84.70
Purchase #4	$70.87	11.419%	$78.9626	$78.96	$78.95	$79.00
Purchase #5	$143.37	5.693%	$151.5321	$151.53	$151.55	$151.50
Purchase #6	$104.74	13.679%	$119.0674	$119.07	$119.05	$119.10
Purchase #7	$51.37	6.482%	$54.6998	$54.70	$54.70	$54.70
7 purchase totals =	$568.34		$626.8996	$626.89	$626.90	$627.00