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	$243.92	4.577%	$255.0842	$255.08	$255.10	$255.10
Purchase #2	$12.32	8.613%	$13.3811	$13.38	$13.40	$13.40
Purchase #3	$225.83	9.401%	$247.0603	$247.06	$247.05	$247.10
Purchase #4	$106.88	5.383%	$112.6334	$112.63	$112.65	$112.60
Purchase #5	$233.75	7.613%	$251.5454	$251.55	$251.55	$251.50
Purchase #6	$42.63	12.610%	$48.0056	$48.01	$48.00	$48.00
Purchase #7	$100.92	12.381%	$113.4149	$113.41	$113.40	$113.40
7 purchase totals =	$966.25		$1,041.1249	$1,041.12	$1,041.15	$1,041.10