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	$89.33	4.784%	$93.6035	$93.60	$93.60	$93.60
Purchase #2	$177.79	7.615%	$191.3287	$191.33	$191.35	$191.30
Purchase #3	$101.87	3.462%	$105.3967	$105.40	$105.40	$105.40
Purchase #4	$116.69	9.683%	$127.9891	$127.99	$128.00	$128.00
Purchase #5	$47.69	5.789%	$50.4508	$50.45	$50.45	$50.50
Purchase #6	$190.86	9.443%	$208.8829	$208.88	$208.90	$208.90
Purchase #7	$41.61	6.720%	$44.4062	$44.41	$44.40	$44.40
7 purchase totals =	$765.84		$822.0579	$822.06	$822.10	$822.10