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	$111.57	7.274%	$119.6856	$119.69	$119.70	$119.70
Purchase #2	$216.34	3.782%	$224.522	$224.52	$224.50	$224.50
Purchase #3	$143.86	13.729%	$163.6105	$163.61	$163.60	$163.60
Purchase #4	$174.87	12.480%	$196.6938	$196.69	$196.70	$196.70
Purchase #5	$155.90	7.674%	$167.8638	$167.86	$167.85	$167.90
Purchase #6	$127.66	9.728%	$140.0788	$140.08	$140.10	$140.10
Purchase #7	$209.30	10.577%	$231.4377	$231.44	$231.45	$231.40
7 purchase totals =	$1,139.50		$1,243.8922	$1,243.89	$1,243.90	$1,243.90