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	$46.90	11.866%	$52.4652	$52.47	$52.45	$52.50
Purchase #2	$52.35	3.707%	$54.2906	$54.29	$54.30	$54.30
Purchase #3	$41.88	8.631%	$45.4947	$45.49	$45.50	$45.50
Purchase #4	$242.26	3.853%	$251.5943	$251.59	$251.60	$251.60
Purchase #5	$221.56	10.315%	$244.4139	$244.41	$244.40	$244.40
Purchase #6	$90.47	3.458%	$93.5985	$93.60	$93.60	$93.60
Purchase #7	$178.29	8.238%	$192.9775	$192.98	$193.00	$193.00
7 purchase totals =	$873.71		$934.8347	$934.83	$934.85	$934.90