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	$187.52	11.681%	$209.4242	$209.42	$209.40	$209.40
Purchase #2	$226.67	12.812%	$255.711	$255.71	$255.70	$255.70
Purchase #3	$105.43	5.650%	$111.3868	$111.39	$111.40	$111.40
Purchase #4	$95.67	10.443%	$105.6608	$105.66	$105.65	$105.70
Purchase #5	$179.35	7.335%	$192.5053	$192.51	$192.50	$192.50
Purchase #6	$37.98	6.142%	$40.3127	$40.31	$40.30	$40.30
Purchase #7	$132.59	3.421%	$137.1259	$137.13	$137.15	$137.10
7 purchase totals =	$965.21		$1,052.1267	$1,052.13	$1,052.10	$1,052.10