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	$41.87	4.380%	$43.7039	$43.70	$43.70	$43.70
Purchase #2	$49.35	11.719%	$55.1333	$55.13	$55.15	$55.10
Purchase #3	$141.70	11.835%	$158.4702	$158.47	$158.45	$158.50
Purchase #4	$45.28	12.495%	$50.9377	$50.94	$50.95	$50.90
Purchase #5	$87.57	8.109%	$94.6711	$94.67	$94.65	$94.70
Purchase #6	$187.52	4.795%	$196.5116	$196.51	$196.50	$196.50
Purchase #7	$8.54	10.486%	$9.4355	$9.44	$9.45	$9.40
7 purchase totals =	$561.83		$608.8633	$608.86	$608.85	$608.80