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	$100.87	10.114%	$111.072	$111.07	$111.05	$111.10
Purchase #2	$46.78	6.145%	$49.6546	$49.65	$49.65	$49.70
Purchase #3	$192.95	11.120%	$214.406	$214.41	$214.40	$214.40
Purchase #4	$85.84	12.162%	$96.2799	$96.28	$96.30	$96.30
Purchase #5	$29.85	9.261%	$32.6144	$32.61	$32.60	$32.60
Purchase #6	$29.68	9.837%	$32.5996	$32.60	$32.60	$32.60
Purchase #7	$176.91	8.184%	$191.3883	$191.39	$191.40	$191.40
7 purchase totals =	$662.88		$728.0148	$728.01	$728.00	$728.10