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	$91.44	13.592%	$103.8685	$103.87	$103.85	$103.90
Purchase #2	$240.77	4.861%	$252.4738	$252.47	$252.45	$252.50
Purchase #3	$55.91	11.687%	$62.4442	$62.44	$62.45	$62.40
Purchase #4	$14.70	10.177%	$16.196	$16.20	$16.20	$16.20
Purchase #5	$107.37	8.831%	$116.8518	$116.85	$116.85	$116.90
Purchase #6	$160.55	13.462%	$182.1632	$182.16	$182.15	$182.20
Purchase #7	$100.32	10.789%	$111.1435	$111.14	$111.15	$111.10
7 purchase totals =	$771.06		$845.1410	$845.13	$845.10	$845.20