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	$161.70	10.203%	$178.1983	$178.20	$178.20	$178.20
Purchase #2	$59.60	4.534%	$62.3023	$62.30	$62.30	$62.30
Purchase #3	$213.41	13.141%	$241.4542	$241.45	$241.45	$241.50
Purchase #4	$35.69	4.678%	$37.3596	$37.36	$37.35	$37.40
Purchase #5	$248.72	9.241%	$271.7042	$271.70	$271.70	$271.70
Purchase #6	$103.95	12.379%	$116.818	$116.82	$116.80	$116.80
Purchase #7	$139.29	9.622%	$152.6925	$152.69	$152.70	$152.70
7 purchase totals =	$962.36		$1,060.5291	$1,060.52	$1,060.50	$1,060.60