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	$147.78	13.116%	$167.1628	$167.16	$167.15	$167.20
Purchase #2	$146.71	11.724%	$163.9103	$163.91	$163.90	$163.90
Purchase #3	$190.41	3.537%	$197.1448	$197.14	$197.15	$197.10
Purchase #4	$91.82	11.511%	$102.3894	$102.39	$102.40	$102.40
Purchase #5	$150.49	3.329%	$155.4998	$155.50	$155.50	$155.50
Purchase #6	$156.33	12.669%	$176.1354	$176.14	$176.15	$176.10
Purchase #7	$111.51	10.761%	$123.5096	$123.51	$123.50	$123.50
7 purchase totals =	$995.05		$1,085.7521	$1,085.75	$1,085.75	$1,085.70