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	$130.33	11.206%	$144.9348	$144.93	$144.95	$144.90
Purchase #2	$81.82	9.314%	$89.4407	$89.44	$89.45	$89.40
Purchase #3	$93.27	4.660%	$97.6164	$97.62	$97.60	$97.60
Purchase #4	$148.43	12.482%	$166.957	$166.96	$166.95	$167.00
Purchase #5	$25.42	7.182%	$27.2457	$27.25	$27.25	$27.20
Purchase #6	$20.86	8.106%	$22.5509	$22.55	$22.55	$22.60
Purchase #7	$100.88	12.708%	$113.6998	$113.70	$113.70	$113.70
7 purchase totals =	$601.01		$662.4453	$662.45	$662.45	$662.40