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	$234.92	9.680%	$257.6603	$257.66	$257.65	$257.70
Purchase #2	$42.61	3.278%	$44.0068	$44.01	$44.00	$44.00
Purchase #3	$223.26	12.143%	$250.3705	$250.37	$250.35	$250.40
Purchase #4	$18.25	12.370%	$20.5075	$20.51	$20.50	$20.50
Purchase #5	$217.87	9.171%	$237.8509	$237.85	$237.85	$237.90
Purchase #6	$86.28	3.716%	$89.4862	$89.49	$89.50	$89.50
Purchase #7	$55.39	12.413%	$62.2656	$62.27	$62.25	$62.30
7 purchase totals =	$878.58		$962.1478	$962.16	$962.10	$962.30