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	$173.43	13.557%	$196.9419	$196.94	$196.95	$196.90
Purchase #2	$125.95	11.821%	$140.8385	$140.84	$140.85	$140.80
Purchase #3	$113.49	8.712%	$123.3772	$123.38	$123.40	$123.40
Purchase #4	$109.67	5.642%	$115.8576	$115.86	$115.85	$115.90
Purchase #5	$50.70	6.422%	$53.956	$53.96	$53.95	$54.00
Purchase #6	$180.85	10.657%	$200.1232	$200.12	$200.10	$200.10
Purchase #7	$43.78	8.191%	$47.366	$47.37	$47.35	$47.40
7 purchase totals =	$797.87		$878.4604	$878.47	$878.45	$878.50