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	$85.96	13.472%	$97.5405	$97.54	$97.55	$97.50
Purchase #2	$215.70	10.636%	$238.6419	$238.64	$238.65	$238.60
Purchase #3	$242.30	7.821%	$261.2503	$261.25	$261.25	$261.30
Purchase #4	$91.51	5.571%	$96.608	$96.61	$96.60	$96.60
Purchase #5	$132.81	5.761%	$140.4612	$140.46	$140.45	$140.50
Purchase #6	$191.31	12.778%	$215.7556	$215.76	$215.75	$215.80
Purchase #7	$137.26	6.493%	$146.1723	$146.17	$146.15	$146.20
7 purchase totals =	$1,096.85		$1,196.4298	$1,196.43	$1,196.40	$1,196.50