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	$200.28	13.603%	$227.5241	$227.52	$227.50	$227.50
Purchase #2	$46.86	13.650%	$53.2564	$53.26	$53.25	$53.30
Purchase #3	$99.88	4.581%	$104.4555	$104.46	$104.45	$104.50
Purchase #4	$7.27	4.422%	$7.5915	$7.59	$7.60	$7.60
Purchase #5	$80.41	6.557%	$85.6825	$85.68	$85.70	$85.70
Purchase #6	$135.91	5.865%	$143.8811	$143.88	$143.90	$143.90
Purchase #7	$121.26	13.246%	$137.3221	$137.32	$137.30	$137.30
7 purchase totals =	$691.87		$759.7132	$759.71	$759.70	$759.80