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	$228.82	11.848%	$255.9306	$255.93	$255.95	$255.90
Purchase #2	$176.98	4.448%	$184.8521	$184.85	$184.85	$184.90
Purchase #3	$61.67	3.735%	$63.9734	$63.97	$63.95	$64.00
Purchase #4	$48.88	11.346%	$54.4259	$54.43	$54.45	$54.40
Purchase #5	$219.97	8.479%	$238.6213	$238.62	$238.60	$238.60
Purchase #6	$164.74	9.513%	$180.4117	$180.41	$180.40	$180.40
Purchase #7	$92.59	7.326%	$99.3731	$99.37	$99.35	$99.40
7 purchase totals =	$993.65		$1,077.5881	$1,077.58	$1,077.55	$1,077.60