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	$213.83	4.448%	$223.3412	$223.34	$223.35	$223.30
Purchase #2	$14.35	8.151%	$15.5197	$15.52	$15.50	$15.50
Purchase #3	$51.89	8.359%	$56.2275	$56.23	$56.25	$56.20
Purchase #4	$62.84	13.710%	$71.4554	$71.46	$71.45	$71.50
Purchase #5	$78.49	5.376%	$82.7096	$82.71	$82.70	$82.70
Purchase #6	$158.48	10.577%	$175.2424	$175.24	$175.25	$175.20
Purchase #7	$23.93	13.864%	$27.2477	$27.25	$27.25	$27.20
7 purchase totals =	$603.81		$651.7435	$651.75	$651.75	$651.60