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	$147.50	7.338%	$158.3236	$158.32	$158.30	$158.30
Purchase #2	$164.52	7.413%	$176.7159	$176.72	$176.70	$176.70
Purchase #3	$115.67	10.288%	$127.5701	$127.57	$127.55	$127.60
Purchase #4	$200.63	9.827%	$220.3459	$220.35	$220.35	$220.30
Purchase #5	$236.28	8.298%	$255.8865	$255.89	$255.90	$255.90
Purchase #6	$28.89	9.417%	$31.6106	$31.61	$31.60	$31.60
Purchase #7	$151.46	10.149%	$166.8317	$166.83	$166.85	$166.80
7 purchase totals =	$1,044.95		$1,137.2843	$1,137.29	$1,137.25	$1,137.20