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	$236.86	10.568%	$261.8914	$261.89	$261.90	$261.90
Purchase #2	$151.67	13.421%	$172.0256	$172.03	$172.05	$172.00
Purchase #3	$88.45	6.799%	$94.4637	$94.46	$94.45	$94.50
Purchase #4	$151.72	12.581%	$170.8079	$170.81	$170.80	$170.80
Purchase #5	$122.65	9.643%	$134.4771	$134.48	$134.50	$134.50
Purchase #6	$154.88	4.636%	$162.0602	$162.06	$162.05	$162.10
Purchase #7	$80.37	3.544%	$83.2183	$83.22	$83.20	$83.20
7 purchase totals =	$986.60		$1,078.9442	$1,078.95	$1,078.95	$1,079.00