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	$241.32	3.317%	$249.3246	$249.32	$249.30	$249.30
Purchase #2	$98.83	12.534%	$111.2174	$111.22	$111.20	$111.20
Purchase #3	$108.32	4.691%	$113.4013	$113.40	$113.40	$113.40
Purchase #4	$224.69	5.198%	$236.3694	$236.37	$236.35	$236.40
Purchase #5	$186.96	10.161%	$205.957	$205.96	$205.95	$206.00
Purchase #6	$56.45	10.337%	$62.2852	$62.29	$62.30	$62.30
Purchase #7	$83.32	5.445%	$87.8568	$87.86	$87.85	$87.90
7 purchase totals =	$999.89		$1,066.4117	$1,066.42	$1,066.35	$1,066.50