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	$215.25	3.151%	$222.0325	$222.03	$222.05	$222.00
Purchase #2	$126.97	13.301%	$143.8583	$143.86	$143.85	$143.90
Purchase #3	$242.51	7.238%	$260.0629	$260.06	$260.05	$260.10
Purchase #4	$180.82	4.364%	$188.711	$188.71	$188.70	$188.70
Purchase #5	$125.67	9.322%	$137.385	$137.39	$137.40	$137.40
Purchase #6	$134.97	10.314%	$148.8908	$148.89	$148.90	$148.90
Purchase #7	$45.45	9.174%	$49.6196	$49.62	$49.60	$49.60
7 purchase totals =	$1,071.64		$1,150.5601	$1,150.56	$1,150.55	$1,150.60