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	$125.82	8.298%	$136.2605	$136.26	$136.25	$136.30
Purchase #2	$158.65	5.567%	$167.482	$167.48	$167.50	$167.50
Purchase #3	$122.68	11.245%	$136.4754	$136.48	$136.50	$136.50
Purchase #4	$203.59	7.149%	$218.1446	$218.14	$218.15	$218.10
Purchase #5	$112.59	3.212%	$116.2064	$116.21	$116.20	$116.20
Purchase #6	$52.55	7.681%	$56.5864	$56.59	$56.60	$56.60
Purchase #7	$227.45	11.845%	$254.3915	$254.39	$254.40	$254.40
7 purchase totals =	$1,003.33		$1,085.5468	$1,085.55	$1,085.60	$1,085.60