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	$205.67	12.240%	$230.844	$230.84	$230.85	$230.80
Purchase #2	$116.89	12.372%	$131.3516	$131.35	$131.35	$131.40
Purchase #3	$99.38	4.810%	$104.1602	$104.16	$104.15	$104.20
Purchase #4	$172.25	11.548%	$192.1414	$192.14	$192.15	$192.10
Purchase #5	$49.60	4.612%	$51.8876	$51.89	$51.90	$51.90
Purchase #6	$191.83	6.697%	$204.6769	$204.68	$204.70	$204.70
Purchase #7	$141.54	7.516%	$152.1781	$152.18	$152.20	$152.20
7 purchase totals =	$977.16		$1,067.2398	$1,067.24	$1,067.30	$1,067.30