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	$33.54	11.373%	$37.3545	$37.35	$37.35	$37.40
Purchase #2	$154.50	5.113%	$162.3996	$162.40	$162.40	$162.40
Purchase #3	$121.97	13.616%	$138.5774	$138.58	$138.60	$138.60
Purchase #4	$107.62	5.810%	$113.8727	$113.87	$113.85	$113.90
Purchase #5	$247.56	3.517%	$256.2667	$256.27	$256.25	$256.30
Purchase #6	$156.86	6.690%	$167.3539	$167.35	$167.35	$167.40
Purchase #7	$237.56	12.268%	$266.7039	$266.70	$266.70	$266.70
7 purchase totals =	$1,059.61		$1,142.5287	$1,142.52	$1,142.50	$1,142.70