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	$114.37	13.670%	$130.0044	$130.00	$130.00	$130.00
Purchase #2	$194.71	7.170%	$208.6707	$208.67	$208.65	$208.70
Purchase #3	$76.78	4.804%	$80.4685	$80.47	$80.45	$80.50
Purchase #4	$57.67	7.518%	$62.0056	$62.01	$62.00	$62.00
Purchase #5	$82.47	3.822%	$85.622	$85.62	$85.60	$85.60
Purchase #6	$49.51	10.195%	$54.5575	$54.56	$54.55	$54.60
Purchase #7	$244.85	9.660%	$268.5025	$268.50	$268.50	$268.50
7 purchase totals =	$820.36		$889.8312	$889.83	$889.75	$889.90