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	$209.83	13.149%	$237.4205	$237.42	$237.40	$237.40
Purchase #2	$106.52	7.701%	$114.7231	$114.72	$114.70	$114.70
Purchase #3	$79.79	3.325%	$82.443	$82.44	$82.45	$82.40
Purchase #4	$159.32	11.414%	$177.5048	$177.50	$177.50	$177.50
Purchase #5	$226.71	6.622%	$241.7227	$241.72	$241.70	$241.70
Purchase #6	$247.75	9.405%	$271.0509	$271.05	$271.05	$271.10
Purchase #7	$63.58	12.495%	$71.5243	$71.52	$71.50	$71.50
7 purchase totals =	$1,093.50		$1,196.3893	$1,196.37	$1,196.30	$1,196.30