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	$118.59	4.136%	$123.4949	$123.49	$123.50	$123.50
Purchase #2	$38.91	9.432%	$42.58	$42.58	$42.60	$42.60
Purchase #3	$88.92	6.231%	$94.4606	$94.46	$94.45	$94.50
Purchase #4	$172.40	8.447%	$186.9626	$186.96	$186.95	$187.00
Purchase #5	$104.64	6.823%	$111.7796	$111.78	$111.80	$111.80
Purchase #6	$249.59	12.770%	$281.4626	$281.46	$281.45	$281.50
Purchase #7	$156.69	12.580%	$176.4016	$176.40	$176.40	$176.40
7 purchase totals =	$929.74		$1,017.1419	$1,017.13	$1,017.15	$1,017.30