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	$87.84	13.324%	$99.5438	$99.54	$99.55	$99.50
Purchase #2	$70.35	11.828%	$78.671	$78.67	$78.65	$78.70
Purchase #3	$76.75	11.475%	$85.5571	$85.56	$85.55	$85.60
Purchase #4	$217.90	4.206%	$227.0649	$227.06	$227.05	$227.10
Purchase #5	$178.96	13.218%	$202.6149	$202.61	$202.60	$202.60
Purchase #6	$181.62	5.515%	$191.6363	$191.64	$191.65	$191.60
Purchase #7	$205.87	9.159%	$224.7256	$224.73	$224.75	$224.70
7 purchase totals =	$1,019.29		$1,109.8136	$1,109.81	$1,109.80	$1,109.80