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	$134.48	13.326%	$152.4008	$152.40	$152.40	$152.40
Purchase #2	$61.95	7.648%	$66.6879	$66.69	$66.70	$66.70
Purchase #3	$225.59	3.761%	$234.0744	$234.07	$234.05	$234.10
Purchase #4	$234.49	9.852%	$257.592	$257.59	$257.60	$257.60
Purchase #5	$79.78	9.401%	$87.2801	$87.28	$87.30	$87.30
Purchase #6	$79.87	11.737%	$89.2443	$89.24	$89.25	$89.20
Purchase #7	$51.84	5.361%	$54.6191	$54.62	$54.60	$54.60
7 purchase totals =	$868.00		$941.8986	$941.89	$941.90	$941.90