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	$153.26	10.631%	$169.5531	$169.55	$169.55	$169.60
Purchase #2	$54.26	10.173%	$59.7799	$59.78	$59.80	$59.80
Purchase #3	$107.39	5.670%	$113.479	$113.48	$113.50	$113.50
Purchase #4	$118.27	9.724%	$129.7706	$129.77	$129.75	$129.80
Purchase #5	$117.53	5.178%	$123.6157	$123.62	$123.60	$123.60
Purchase #6	$139.85	3.357%	$144.5448	$144.54	$144.55	$144.50
Purchase #7	$182.81	3.186%	$188.6343	$188.63	$188.65	$188.60
7 purchase totals =	$873.37		$929.3774	$929.37	$929.40	$929.40