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	$83.95	7.656%	$90.3772	$90.38	$90.40	$90.40
Purchase #2	$24.47	13.600%	$27.7979	$27.80	$27.80	$27.80
Purchase #3	$40.79	9.635%	$44.7201	$44.72	$44.70	$44.70
Purchase #4	$186.39	4.746%	$195.2361	$195.24	$195.25	$195.20
Purchase #5	$39.93	6.699%	$42.6049	$42.60	$42.60	$42.60
Purchase #6	$60.32	8.238%	$65.2892	$65.29	$65.30	$65.30
Purchase #7	$6.53	4.162%	$6.8018	$6.80	$6.80	$6.80
7 purchase totals =	$442.38		$472.8272	$472.83	$472.85	$472.80