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	$226.86	6.173%	$240.8641	$240.86	$240.85	$240.90
Purchase #2	$76.83	12.822%	$86.6811	$86.68	$86.70	$86.70
Purchase #3	$10.32	11.166%	$11.4723	$11.47	$11.45	$11.50
Purchase #4	$113.84	4.697%	$119.1871	$119.19	$119.20	$119.20
Purchase #5	$222.67	9.715%	$244.3024	$244.30	$244.30	$244.30
Purchase #6	$221.39	4.260%	$230.8212	$230.82	$230.80	$230.80
Purchase #7	$101.81	9.708%	$111.6937	$111.69	$111.70	$111.70
7 purchase totals =	$973.72		$1,045.0219	$1,045.01	$1,045.00	$1,045.10