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	$48.40	4.696%	$50.6729	$50.67	$50.65	$50.70
Purchase #2	$152.83	10.621%	$169.0621	$169.06	$169.05	$169.10
Purchase #3	$123.79	11.141%	$137.5814	$137.58	$137.60	$137.60
Purchase #4	$42.86	9.189%	$46.7984	$46.80	$46.80	$46.80
Purchase #5	$85.82	11.371%	$95.5786	$95.58	$95.60	$95.60
Purchase #6	$143.41	7.139%	$153.648	$153.65	$153.65	$153.60
Purchase #7	$135.70	8.529%	$147.2739	$147.27	$147.25	$147.30
7 purchase totals =	$732.81		$800.6153	$800.61	$800.60	$800.70