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	$48.69	12.186%	$54.6234	$54.62	$54.60	$54.60
Purchase #2	$51.42	10.739%	$56.942	$56.94	$56.95	$56.90
Purchase #3	$221.35	10.529%	$244.6559	$244.66	$244.65	$244.70
Purchase #4	$136.88	6.811%	$146.2029	$146.20	$146.20	$146.20
Purchase #5	$94.94	5.804%	$100.4503	$100.45	$100.45	$100.50
Purchase #6	$162.37	11.534%	$181.0978	$181.10	$181.10	$181.10
Purchase #7	$225.50	8.573%	$244.8321	$244.83	$244.85	$244.80
7 purchase totals =	$941.15		$1,028.8044	$1,028.80	$1,028.80	$1,028.80