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	$192.60	11.152%	$214.0788	$214.08	$214.10	$214.10
Purchase #2	$138.61	11.726%	$154.8634	$154.86	$154.85	$154.90
Purchase #3	$178.87	6.691%	$190.8382	$190.84	$190.85	$190.80
Purchase #4	$44.91	5.420%	$47.3441	$47.34	$47.35	$47.30
Purchase #5	$78.67	13.371%	$89.189	$89.19	$89.20	$89.20
Purchase #6	$75.75	6.366%	$80.5722	$80.57	$80.55	$80.60
Purchase #7	$144.84	13.727%	$164.7222	$164.72	$164.70	$164.70
7 purchase totals =	$854.25		$941.6079	$941.60	$941.60	$941.60