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	$94.37	3.522%	$97.6937	$97.69	$97.70	$97.70
Purchase #2	$134.35	13.535%	$152.5343	$152.53	$152.55	$152.50
Purchase #3	$46.67	12.738%	$52.6148	$52.61	$52.60	$52.60
Purchase #4	$123.52	11.136%	$137.2752	$137.28	$137.30	$137.30
Purchase #5	$238.72	6.835%	$255.0365	$255.04	$255.05	$255.00
Purchase #6	$230.94	3.212%	$238.3578	$238.36	$238.35	$238.40
Purchase #7	$120.72	4.587%	$126.2574	$126.26	$126.25	$126.30
7 purchase totals =	$989.29		$1,059.7697	$1,059.77	$1,059.80	$1,059.80