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	$248.52	3.182%	$256.4279	$256.43	$256.45	$256.40
Purchase #2	$111.34	13.167%	$126.0001	$126.00	$126.00	$126.00
Purchase #3	$18.63	3.421%	$19.2673	$19.27	$19.25	$19.30
Purchase #4	$106.77	7.159%	$114.4137	$114.41	$114.40	$114.40
Purchase #5	$213.52	11.258%	$237.5581	$237.56	$237.55	$237.60
Purchase #6	$228.96	12.186%	$256.8611	$256.86	$256.85	$256.90
Purchase #7	$87.49	13.222%	$99.0579	$99.06	$99.05	$99.10
7 purchase totals =	$1,015.23		$1,109.5861	$1,109.59	$1,109.55	$1,109.70