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	$103.96	4.575%	$108.7162	$108.72	$108.70	$108.70
Purchase #2	$63.63	12.281%	$71.4444	$71.44	$71.45	$71.40
Purchase #3	$163.67	13.291%	$185.4234	$185.42	$185.40	$185.40
Purchase #4	$166.27	12.687%	$187.3647	$187.36	$187.35	$187.40
Purchase #5	$176.74	5.189%	$185.911	$185.91	$185.90	$185.90
Purchase #6	$168.72	10.552%	$186.5233	$186.52	$186.50	$186.50
Purchase #7	$244.40	10.771%	$270.7243	$270.72	$270.70	$270.70
7 purchase totals =	$1,087.39		$1,196.1073	$1,196.09	$1,196.00	$1,196.00