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	$140.41	8.675%	$152.5906	$152.59	$152.60	$152.60
Purchase #2	$196.54	9.727%	$215.6574	$215.66	$215.65	$215.70
Purchase #3	$136.89	5.375%	$144.2478	$144.25	$144.25	$144.20
Purchase #4	$130.51	6.310%	$138.7452	$138.75	$138.75	$138.70
Purchase #5	$132.46	4.152%	$137.9597	$137.96	$137.95	$138.00
Purchase #6	$111.72	5.254%	$117.5898	$117.59	$117.60	$117.60
Purchase #7	$51.52	9.685%	$56.5097	$56.51	$56.50	$56.50
7 purchase totals =	$900.05		$963.3002	$963.31	$963.30	$963.30