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	$79.38	8.215%	$85.9011	$85.90	$85.90	$85.90
Purchase #2	$20.78	3.631%	$21.5345	$21.53	$21.55	$21.50
Purchase #3	$107.70	7.423%	$115.6946	$115.69	$115.70	$115.70
Purchase #4	$152.82	12.203%	$171.4686	$171.47	$171.45	$171.50
Purchase #5	$176.84	7.463%	$190.0376	$190.04	$190.05	$190.00
Purchase #6	$93.64	10.146%	$103.1407	$103.14	$103.15	$103.10
Purchase #7	$141.33	10.211%	$155.7612	$155.76	$155.75	$155.80
7 purchase totals =	$772.49		$843.5383	$843.53	$843.55	$843.50