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	$87.32	4.811%	$91.521	$91.52	$91.50	$91.50
Purchase #2	$51.92	10.419%	$57.3295	$57.33	$57.35	$57.30
Purchase #3	$115.80	5.575%	$122.2559	$122.26	$122.25	$122.30
Purchase #4	$198.25	10.831%	$219.7225	$219.72	$219.70	$219.70
Purchase #5	$231.35	10.244%	$255.0495	$255.05	$255.05	$255.00
Purchase #6	$131.89	9.845%	$144.8746	$144.87	$144.85	$144.90
Purchase #7	$140.58	10.107%	$154.7884	$154.79	$154.80	$154.80
7 purchase totals =	$957.11		$1,045.5414	$1,045.54	$1,045.50	$1,045.50