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	$237.38	9.680%	$260.3584	$260.36	$260.35	$260.40
Purchase #2	$99.87	3.306%	$103.1717	$103.17	$103.15	$103.20
Purchase #3	$39.72	8.713%	$43.1808	$43.18	$43.20	$43.20
Purchase #4	$44.37	9.336%	$48.5124	$48.51	$48.50	$48.50
Purchase #5	$103.55	4.826%	$108.5473	$108.55	$108.55	$108.50
Purchase #6	$173.92	7.682%	$187.2805	$187.28	$187.30	$187.30
Purchase #7	$52.75	12.786%	$59.4946	$59.49	$59.50	$59.50
7 purchase totals =	$751.56		$810.5457	$810.54	$810.55	$810.60