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	$149.43	4.689%	$156.4368	$156.44	$156.45	$156.40
Purchase #2	$149.85	5.783%	$158.5158	$158.52	$158.50	$158.50
Purchase #3	$103.87	9.775%	$114.0233	$114.02	$114.00	$114.00
Purchase #4	$83.57	8.678%	$90.8222	$90.82	$90.80	$90.80
Purchase #5	$182.32	5.171%	$191.7478	$191.75	$191.75	$191.70
Purchase #6	$150.61	9.195%	$164.4586	$164.46	$164.45	$164.50
Purchase #7	$213.37	6.452%	$227.1366	$227.14	$227.15	$227.10
7 purchase totals =	$1,033.02		$1,103.1411	$1,103.15	$1,103.10	$1,103.00