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	$119.62	6.858%	$127.8235	$127.82	$127.80	$127.80
Purchase #2	$56.64	10.414%	$62.5385	$62.54	$62.55	$62.50
Purchase #3	$184.98	8.109%	$199.98	$199.98	$200.00	$200.00
Purchase #4	$46.38	4.422%	$48.4309	$48.43	$48.45	$48.40
Purchase #5	$78.68	3.526%	$81.4543	$81.45	$81.45	$81.50
Purchase #6	$113.48	12.549%	$127.7206	$127.72	$127.70	$127.70
Purchase #7	$92.47	13.188%	$104.6649	$104.66	$104.65	$104.70
7 purchase totals =	$692.25		$752.6127	$752.60	$752.60	$752.60