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	$50.36	5.771%	$53.2663	$53.27	$53.25	$53.30
Purchase #2	$241.27	7.680%	$259.7995	$259.80	$259.80	$259.80
Purchase #3	$34.40	11.659%	$38.4107	$38.41	$38.40	$38.40
Purchase #4	$119.35	3.696%	$123.7612	$123.76	$123.75	$123.80
Purchase #5	$233.32	12.195%	$261.7734	$261.77	$261.75	$261.80
Purchase #6	$93.82	8.485%	$101.7806	$101.78	$101.80	$101.80
Purchase #7	$14.31	10.809%	$15.8568	$15.86	$15.85	$15.90
7 purchase totals =	$786.83		$854.6485	$854.65	$854.60	$854.80