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	$116.46	6.151%	$123.6235	$123.62	$123.60	$123.60
Purchase #2	$245.70	5.808%	$259.9703	$259.97	$259.95	$260.00
Purchase #3	$74.94	5.506%	$79.0662	$79.07	$79.05	$79.10
Purchase #4	$183.71	4.231%	$191.4828	$191.48	$191.50	$191.50
Purchase #5	$145.87	4.537%	$152.4881	$152.49	$152.50	$152.50
Purchase #6	$75.54	9.792%	$82.9369	$82.94	$82.95	$82.90
Purchase #7	$212.50	5.707%	$224.6274	$224.63	$224.65	$224.60
7 purchase totals =	$1,054.72		$1,114.1952	$1,114.20	$1,114.20	$1,114.20