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	$147.37	9.175%	$160.8912	$160.89	$160.90	$160.90
Purchase #2	$190.75	4.377%	$199.0991	$199.10	$199.10	$199.10
Purchase #3	$218.39	10.761%	$241.8909	$241.89	$241.90	$241.90
Purchase #4	$232.50	9.850%	$255.4013	$255.40	$255.40	$255.40
Purchase #5	$195.65	5.779%	$206.9566	$206.96	$206.95	$207.00
Purchase #6	$217.75	9.515%	$238.4689	$238.47	$238.45	$238.50
Purchase #7	$111.30	13.476%	$126.2988	$126.30	$126.30	$126.30
7 purchase totals =	$1,313.71		$1,429.0068	$1,429.01	$1,429.00	$1,429.10