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	$149.42	12.737%	$168.4516	$168.45	$168.45	$168.50
Purchase #2	$56.84	7.169%	$60.9149	$60.91	$60.90	$60.90
Purchase #3	$37.65	4.427%	$39.3168	$39.32	$39.30	$39.30
Purchase #4	$244.67	3.264%	$252.656	$252.66	$252.65	$252.70
Purchase #5	$207.46	7.437%	$222.8888	$222.89	$222.90	$222.90
Purchase #6	$153.59	10.243%	$169.3222	$169.32	$169.30	$169.30
Purchase #7	$182.25	5.562%	$192.3867	$192.39	$192.40	$192.40
7 purchase totals =	$1,031.88		$1,105.9370	$1,105.94	$1,105.90	$1,106.00