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	$209.37	13.488%	$237.6098	$237.61	$237.60	$237.60
Purchase #2	$58.83	10.350%	$64.9189	$64.92	$64.90	$64.90
Purchase #3	$246.36	4.205%	$256.7194	$256.72	$256.70	$256.70
Purchase #4	$88.78	13.205%	$100.5034	$100.50	$100.50	$100.50
Purchase #5	$238.69	13.215%	$270.2329	$270.23	$270.25	$270.20
Purchase #6	$53.88	4.584%	$56.3499	$56.35	$56.35	$56.30
Purchase #7	$66.97	5.742%	$70.8154	$70.82	$70.80	$70.80
7 purchase totals =	$962.88		$1,057.1497	$1,057.15	$1,057.10	$1,057.00