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	$180.90	8.739%	$196.7089	$196.71	$196.70	$196.70
Purchase #2	$231.64	10.454%	$255.8556	$255.86	$255.85	$255.90
Purchase #3	$42.27	7.333%	$45.3697	$45.37	$45.35	$45.40
Purchase #4	$122.98	13.141%	$139.1408	$139.14	$139.15	$139.10
Purchase #5	$102.42	9.167%	$111.8088	$111.81	$111.80	$111.80
Purchase #6	$238.39	10.194%	$262.6915	$262.69	$262.70	$262.70
Purchase #7	$215.40	3.470%	$222.8744	$222.87	$222.85	$222.90
7 purchase totals =	$1,134.00		$1,234.4497	$1,234.45	$1,234.40	$1,234.50