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	$246.38	5.834%	$260.7538	$260.75	$260.75	$260.80
Purchase #2	$201.80	10.253%	$222.4906	$222.49	$222.50	$222.50
Purchase #3	$100.90	3.521%	$104.4527	$104.45	$104.45	$104.50
Purchase #4	$32.71	6.430%	$34.8133	$34.81	$34.80	$34.80
Purchase #5	$84.59	6.393%	$89.9978	$90.00	$90.00	$90.00
Purchase #6	$132.64	7.647%	$142.783	$142.78	$142.80	$142.80
Purchase #7	$184.49	4.553%	$192.8898	$192.89	$192.90	$192.90
7 purchase totals =	$983.51		$1,048.1810	$1,048.17	$1,048.20	$1,048.30