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	$238.48	9.536%	$261.2215	$261.22	$261.20	$261.20
Purchase #2	$69.89	13.451%	$79.2909	$79.29	$79.30	$79.30
Purchase #3	$215.50	5.387%	$227.109	$227.11	$227.10	$227.10
Purchase #4	$145.64	13.179%	$164.8339	$164.83	$164.85	$164.80
Purchase #5	$173.91	7.102%	$186.2611	$186.26	$186.25	$186.30
Purchase #6	$106.26	5.291%	$111.8822	$111.88	$111.90	$111.90
Purchase #7	$16.61	8.381%	$18.0021	$18.00	$18.00	$18.00
7 purchase totals =	$966.29		$1,048.6007	$1,048.59	$1,048.60	$1,048.60