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	$153.58	10.335%	$169.4525	$169.45	$169.45	$169.50
Purchase #2	$245.35	4.715%	$256.9183	$256.92	$256.90	$256.90
Purchase #3	$150.60	12.698%	$169.7232	$169.72	$169.70	$169.70
Purchase #4	$34.35	10.398%	$37.9217	$37.92	$37.90	$37.90
Purchase #5	$98.37	7.203%	$105.4556	$105.46	$105.45	$105.50
Purchase #6	$231.48	13.278%	$262.2159	$262.22	$262.20	$262.20
Purchase #7	$109.56	4.229%	$114.1933	$114.19	$114.20	$114.20
7 purchase totals =	$1,023.29		$1,115.8805	$1,115.88	$1,115.80	$1,115.90