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	$241.81	8.302%	$261.8851	$261.89	$261.90	$261.90
Purchase #2	$25.92	11.507%	$28.9026	$28.90	$28.90	$28.90
Purchase #3	$126.47	12.374%	$142.1194	$142.12	$142.10	$142.10
Purchase #4	$85.79	3.301%	$88.6219	$88.62	$88.60	$88.60
Purchase #5	$132.64	3.355%	$137.0901	$137.09	$137.10	$137.10
Purchase #6	$217.42	4.679%	$227.5931	$227.59	$227.60	$227.60
Purchase #7	$228.31	13.418%	$258.9446	$258.94	$258.95	$258.90
7 purchase totals =	$1,058.36		$1,145.1568	$1,145.15	$1,145.15	$1,145.10