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	$119.94	11.112%	$133.2677	$133.27	$133.25	$133.30
Purchase #2	$98.38	7.382%	$105.6424	$105.64	$105.65	$105.60
Purchase #3	$205.47	10.740%	$227.5375	$227.54	$227.55	$227.50
Purchase #4	$109.35	7.782%	$117.8596	$117.86	$117.85	$117.90
Purchase #5	$74.84	4.244%	$78.0162	$78.02	$78.00	$78.00
Purchase #6	$47.39	9.217%	$51.7579	$51.76	$51.75	$51.80
Purchase #7	$37.75	10.223%	$41.6092	$41.61	$41.60	$41.60
7 purchase totals =	$693.12		$755.6905	$755.70	$755.65	$755.70