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	$158.45	3.333%	$163.7311	$163.73	$163.75	$163.70
Purchase #2	$225.67	13.666%	$256.5101	$256.51	$256.50	$256.50
Purchase #3	$173.63	13.175%	$196.5058	$196.51	$196.50	$196.50
Purchase #4	$113.82	8.588%	$123.5949	$123.59	$123.60	$123.60
Purchase #5	$105.40	6.253%	$111.9907	$111.99	$112.00	$112.00
Purchase #6	$151.43	4.325%	$157.9793	$157.98	$158.00	$158.00
Purchase #7	$7.50	5.706%	$7.928	$7.93	$7.95	$7.90
7 purchase totals =	$935.90		$1,018.2399	$1,018.24	$1,018.30	$1,018.20