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	$153.65	13.563%	$174.4895	$174.49	$174.50	$174.50
Purchase #2	$100.32	12.774%	$113.1349	$113.13	$113.15	$113.10
Purchase #3	$190.87	9.762%	$209.5027	$209.50	$209.50	$209.50
Purchase #4	$108.77	12.871%	$122.7698	$122.77	$122.75	$122.80
Purchase #5	$233.89	9.188%	$255.3798	$255.38	$255.40	$255.40
Purchase #6	$153.83	12.751%	$173.4449	$173.44	$173.45	$173.40
Purchase #7	$104.45	6.276%	$111.0053	$111.01	$111.00	$111.00
7 purchase totals =	$1,045.78		$1,159.7269	$1,159.72	$1,159.75	$1,159.70