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	$111.72	4.706%	$116.9775	$116.98	$117.00	$117.00
Purchase #2	$96.50	4.215%	$100.5675	$100.57	$100.55	$100.60
Purchase #3	$45.35	7.678%	$48.832	$48.83	$48.85	$48.80
Purchase #4	$95.65	5.346%	$100.7634	$100.76	$100.75	$100.80
Purchase #5	$187.44	10.336%	$206.8138	$206.81	$206.80	$206.80
Purchase #6	$19.79	10.780%	$21.9234	$21.92	$21.90	$21.90
Purchase #7	$187.60	10.253%	$206.8346	$206.83	$206.85	$206.80
7 purchase totals =	$744.05		$802.7122	$802.70	$802.70	$802.70