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	$163.43	12.388%	$183.6757	$183.68	$183.70	$183.70
Purchase #2	$67.77	10.462%	$74.8601	$74.86	$74.85	$74.90
Purchase #3	$69.28	13.321%	$78.5088	$78.51	$78.50	$78.50
Purchase #4	$73.98	7.509%	$79.5352	$79.54	$79.55	$79.50
Purchase #5	$221.92	5.818%	$234.8313	$234.83	$234.85	$234.80
Purchase #6	$88.76	10.677%	$98.2369	$98.24	$98.25	$98.20
Purchase #7	$33.42	12.150%	$37.4805	$37.48	$37.50	$37.50
7 purchase totals =	$718.56		$787.1285	$787.14	$787.20	$787.10