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	$205.30	5.252%	$216.0824	$216.08	$216.10	$216.10
Purchase #2	$131.72	11.170%	$146.4331	$146.43	$146.45	$146.40
Purchase #3	$75.72	11.501%	$84.4286	$84.43	$84.45	$84.40
Purchase #4	$41.53	9.779%	$45.5912	$45.59	$45.60	$45.60
Purchase #5	$96.31	4.396%	$100.5438	$100.54	$100.55	$100.50
Purchase #6	$208.59	10.694%	$230.8966	$230.90	$230.90	$230.90
Purchase #7	$109.70	4.132%	$114.2328	$114.23	$114.25	$114.20
7 purchase totals =	$868.87		$938.2085	$938.20	$938.30	$938.10