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	$212.95	10.813%	$235.9763	$235.98	$236.00	$236.00
Purchase #2	$54.90	12.831%	$61.9442	$61.94	$61.95	$61.90
Purchase #3	$131.45	6.141%	$139.5223	$139.52	$139.50	$139.50
Purchase #4	$20.80	4.569%	$21.7504	$21.75	$21.75	$21.80
Purchase #5	$90.51	13.239%	$102.4926	$102.49	$102.50	$102.50
Purchase #6	$135.31	12.173%	$151.7813	$151.78	$151.80	$151.80
Purchase #7	$53.36	10.682%	$59.0599	$59.06	$59.05	$59.10
7 purchase totals =	$699.28		$772.5270	$772.52	$772.55	$772.60