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	$87.82	4.221%	$91.5269	$91.53	$91.55	$91.50
Purchase #2	$227.29	11.105%	$252.5306	$252.53	$252.55	$252.50
Purchase #3	$239.69	5.210%	$252.1778	$252.18	$252.20	$252.20
Purchase #4	$64.31	10.146%	$70.8349	$70.83	$70.85	$70.80
Purchase #5	$157.93	5.147%	$166.0587	$166.06	$166.05	$166.10
Purchase #6	$72.33	8.711%	$78.6307	$78.63	$78.65	$78.60
Purchase #7	$145.85	3.360%	$150.7506	$150.75	$150.75	$150.80
7 purchase totals =	$995.22		$1,062.5102	$1,062.51	$1,062.60	$1,062.50