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	$54.62	9.119%	$59.6008	$59.60	$59.60	$59.60
Purchase #2	$222.56	13.634%	$252.9038	$252.90	$252.90	$252.90
Purchase #3	$143.76	11.315%	$160.0264	$160.03	$160.05	$160.00
Purchase #4	$5.67	3.469%	$5.8667	$5.87	$5.85	$5.90
Purchase #5	$246.91	8.357%	$267.5443	$267.54	$267.55	$267.50
Purchase #6	$170.32	11.821%	$190.4535	$190.45	$190.45	$190.50
Purchase #7	$229.67	11.492%	$256.0637	$256.06	$256.05	$256.10
7 purchase totals =	$1,073.51		$1,192.4592	$1,192.45	$1,192.45	$1,192.50