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	$187.66	12.378%	$210.8886	$210.89	$210.90	$210.90
Purchase #2	$44.40	3.220%	$45.8297	$45.83	$45.85	$45.80
Purchase #3	$192.98	11.520%	$215.2113	$215.21	$215.20	$215.20
Purchase #4	$248.59	5.302%	$261.7702	$261.77	$261.75	$261.80
Purchase #5	$87.68	9.794%	$96.2674	$96.27	$96.25	$96.30
Purchase #6	$240.72	6.119%	$255.4497	$255.45	$255.45	$255.40
Purchase #7	$205.40	3.255%	$212.0858	$212.09	$212.10	$212.10
7 purchase totals =	$1,207.43		$1,297.5027	$1,297.51	$1,297.50	$1,297.50