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	$140.49	3.145%	$144.9084	$144.91	$144.90	$144.90
Purchase #2	$65.64	3.196%	$67.7379	$67.74	$67.75	$67.70
Purchase #3	$111.38	13.441%	$126.3506	$126.35	$126.35	$126.40
Purchase #4	$160.77	4.715%	$168.3503	$168.35	$168.35	$168.40
Purchase #5	$13.55	4.395%	$14.1455	$14.15	$14.15	$14.10
Purchase #6	$100.93	4.648%	$105.6212	$105.62	$105.60	$105.60
Purchase #7	$65.86	5.557%	$69.5198	$69.52	$69.50	$69.50
7 purchase totals =	$658.62		$696.6337	$696.64	$696.60	$696.60