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	$100.27	5.687%	$105.9724	$105.97	$105.95	$106.00
Purchase #2	$118.31	4.615%	$123.77	$123.77	$123.75	$123.80
Purchase #3	$134.27	13.300%	$152.1279	$152.13	$152.15	$152.10
Purchase #4	$216.93	8.528%	$235.4298	$235.43	$235.45	$235.40
Purchase #5	$124.41	9.735%	$136.5213	$136.52	$136.50	$136.50
Purchase #6	$13.91	6.724%	$14.8453	$14.85	$14.85	$14.80
Purchase #7	$136.89	4.844%	$143.521	$143.52	$143.50	$143.50
7 purchase totals =	$844.99		$912.1877	$912.19	$912.15	$912.10