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	$90.64	9.650%	$99.3868	$99.39	$99.40	$99.40
Purchase #2	$107.37	6.213%	$114.0409	$114.04	$114.05	$114.00
Purchase #3	$149.58	11.283%	$166.4571	$166.46	$166.45	$166.50
Purchase #4	$76.34	7.747%	$82.2541	$82.25	$82.25	$82.30
Purchase #5	$101.45	13.297%	$114.9398	$114.94	$114.95	$114.90
Purchase #6	$238.82	6.303%	$253.8728	$253.87	$253.85	$253.90
Purchase #7	$63.64	12.827%	$71.8031	$71.80	$71.80	$71.80
7 purchase totals =	$827.84		$902.7546	$902.75	$902.75	$902.80