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	$58.96	11.466%	$65.7204	$65.72	$65.70	$65.70
Purchase #2	$148.65	6.547%	$158.3821	$158.38	$158.40	$158.40
Purchase #3	$190.61	13.476%	$216.2966	$216.30	$216.30	$216.30
Purchase #4	$40.31	6.745%	$43.0289	$43.03	$43.05	$43.00
Purchase #5	$29.82	7.116%	$31.942	$31.94	$31.95	$31.90
Purchase #6	$40.52	10.240%	$44.6692	$44.67	$44.65	$44.70
Purchase #7	$40.77	8.654%	$44.2982	$44.30	$44.30	$44.30
7 purchase totals =	$549.64		$604.3374	$604.34	$604.35	$604.30