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	$17.82	9.163%	$19.4528	$19.45	$19.45	$19.50
Purchase #2	$59.90	3.389%	$61.93	$61.93	$61.95	$61.90
Purchase #3	$38.96	3.672%	$40.3906	$40.39	$40.40	$40.40
Purchase #4	$52.45	5.446%	$55.3064	$55.31	$55.30	$55.30
Purchase #5	$224.66	7.544%	$241.6084	$241.61	$241.60	$241.60
Purchase #6	$204.37	11.523%	$227.9196	$227.92	$227.90	$227.90
Purchase #7	$207.49	10.391%	$229.0503	$229.05	$229.05	$229.10
7 purchase totals =	$805.65		$875.6581	$875.66	$875.65	$875.70