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	$156.62	12.276%	$175.8467	$175.85	$175.85	$175.80
Purchase #2	$49.68	8.454%	$53.8799	$53.88	$53.90	$53.90
Purchase #3	$202.90	11.739%	$226.7184	$226.72	$226.70	$226.70
Purchase #4	$194.93	10.495%	$215.3879	$215.39	$215.40	$215.40
Purchase #5	$167.57	3.804%	$173.9444	$173.94	$173.95	$173.90
Purchase #6	$88.68	6.156%	$94.1391	$94.14	$94.15	$94.10
Purchase #7	$239.62	7.136%	$256.7193	$256.72	$256.70	$256.70
7 purchase totals =	$1,100.00		$1,196.6357	$1,196.64	$1,196.65	$1,196.50