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	$44.68	10.440%	$49.3446	$49.34	$49.35	$49.30
Purchase #2	$45.42	9.184%	$49.5914	$49.59	$49.60	$49.60
Purchase #3	$53.91	6.628%	$57.4832	$57.48	$57.50	$57.50
Purchase #4	$137.50	4.157%	$143.2159	$143.22	$143.20	$143.20
Purchase #5	$137.71	7.177%	$147.5934	$147.59	$147.60	$147.60
Purchase #6	$235.81	5.266%	$248.2278	$248.23	$248.25	$248.20
Purchase #7	$123.44	3.253%	$127.4555	$127.46	$127.45	$127.50
7 purchase totals =	$778.47		$822.9118	$822.91	$822.95	$822.90