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	$159.81	13.861%	$181.9613	$181.96	$181.95	$182.00
Purchase #2	$115.25	3.843%	$119.6791	$119.68	$119.70	$119.70
Purchase #3	$79.93	7.383%	$85.8312	$85.83	$85.85	$85.80
Purchase #4	$126.40	8.518%	$137.1668	$137.17	$137.15	$137.20
Purchase #5	$90.81	13.854%	$103.3908	$103.39	$103.40	$103.40
Purchase #6	$100.25	9.178%	$109.4509	$109.45	$109.45	$109.50
Purchase #7	$118.26	5.308%	$124.5372	$124.54	$124.55	$124.50
7 purchase totals =	$790.71		$862.0173	$862.02	$862.05	$862.10