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	$120.38	9.458%	$131.7655	$131.77	$131.75	$131.80
Purchase #2	$208.95	6.406%	$222.3353	$222.34	$222.35	$222.30
Purchase #3	$241.37	11.746%	$269.7213	$269.72	$269.70	$269.70
Purchase #4	$43.79	13.868%	$49.8628	$49.86	$49.85	$49.90
Purchase #5	$235.67	13.483%	$267.4454	$267.45	$267.45	$267.40
Purchase #6	$230.58	13.728%	$262.234	$262.23	$262.25	$262.20
Purchase #7	$131.27	11.467%	$146.3227	$146.32	$146.30	$146.30
7 purchase totals =	$1,212.01		$1,349.6870	$1,349.69	$1,349.65	$1,349.60