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	$181.29	13.268%	$205.3436	$205.34	$205.35	$205.30
Purchase #2	$127.86	4.750%	$133.9334	$133.93	$133.95	$133.90
Purchase #3	$185.58	5.629%	$196.0263	$196.03	$196.05	$196.00
Purchase #4	$54.94	13.518%	$62.3668	$62.37	$62.35	$62.40
Purchase #5	$118.89	11.367%	$132.4042	$132.40	$132.40	$132.40
Purchase #6	$6.48	13.548%	$7.3579	$7.36	$7.35	$7.40
Purchase #7	$223.50	3.598%	$231.5415	$231.54	$231.55	$231.50
7 purchase totals =	$898.54		$968.9737	$968.97	$969.00	$968.90