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	$67.43	9.396%	$73.7657	$73.77	$73.75	$73.80
Purchase #2	$245.88	5.351%	$259.037	$259.04	$259.05	$259.00
Purchase #3	$232.77	3.260%	$240.3583	$240.36	$240.35	$240.40
Purchase #4	$67.42	12.866%	$76.0943	$76.09	$76.10	$76.10
Purchase #5	$223.89	4.233%	$233.3673	$233.37	$233.35	$233.40
Purchase #6	$121.27	5.308%	$127.707	$127.71	$127.70	$127.70
Purchase #7	$43.57	13.203%	$49.3225	$49.32	$49.30	$49.30
7 purchase totals =	$1,002.23		$1,059.6521	$1,059.66	$1,059.60	$1,059.70