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	$105.37	5.770%	$111.4498	$111.45	$111.45	$111.40
Purchase #2	$190.94	6.855%	$204.0289	$204.03	$204.05	$204.00
Purchase #3	$101.41	3.495%	$104.9543	$104.95	$104.95	$105.00
Purchase #4	$198.52	11.756%	$221.858	$221.86	$221.85	$221.90
Purchase #5	$185.73	3.678%	$192.5611	$192.56	$192.55	$192.60
Purchase #6	$66.61	9.484%	$72.9273	$72.93	$72.95	$72.90
Purchase #7	$59.61	8.130%	$64.4563	$64.46	$64.45	$64.50
7 purchase totals =	$908.19		$972.2357	$972.24	$972.25	$972.30