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	$143.97	8.758%	$156.5789	$156.58	$156.60	$156.60
Purchase #2	$183.41	7.710%	$197.5509	$197.55	$197.55	$197.60
Purchase #3	$156.62	10.766%	$173.4817	$173.48	$173.50	$173.50
Purchase #4	$40.44	5.118%	$42.5097	$42.51	$42.50	$42.50
Purchase #5	$94.29	4.121%	$98.1757	$98.18	$98.20	$98.20
Purchase #6	$248.66	13.647%	$282.5946	$282.59	$282.60	$282.60
Purchase #7	$182.61	12.611%	$205.6389	$205.64	$205.65	$205.60
7 purchase totals =	$1,050.00		$1,156.5304	$1,156.53	$1,156.60	$1,156.60