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	$247.44	7.721%	$266.5448	$266.54	$266.55	$266.50
Purchase #2	$10.41	6.640%	$11.1012	$11.10	$11.10	$11.10
Purchase #3	$218.72	3.548%	$226.4802	$226.48	$226.50	$226.50
Purchase #4	$22.81	12.149%	$25.5812	$25.58	$25.60	$25.60
Purchase #5	$197.68	12.500%	$222.39	$222.39	$222.40	$222.40
Purchase #6	$63.97	13.373%	$72.5247	$72.52	$72.50	$72.50
Purchase #7	$204.88	5.569%	$216.2898	$216.29	$216.30	$216.30
7 purchase totals =	$965.91		$1,040.9119	$1,040.90	$1,040.95	$1,040.90