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	$120.68	9.338%	$131.9491	$131.95	$131.95	$131.90
Purchase #2	$106.94	6.863%	$114.2793	$114.28	$114.30	$114.30
Purchase #3	$180.29	7.192%	$193.2565	$193.26	$193.25	$193.30
Purchase #4	$180.31	10.616%	$199.4517	$199.45	$199.45	$199.50
Purchase #5	$95.64	4.733%	$100.1666	$100.17	$100.15	$100.20
Purchase #6	$118.40	4.670%	$123.9293	$123.93	$123.95	$123.90
Purchase #7	$46.64	10.128%	$51.3637	$51.36	$51.35	$51.40
7 purchase totals =	$848.90		$914.3962	$914.40	$914.40	$914.50