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	$215.54	4.316%	$224.8427	$224.84	$224.85	$224.80
Purchase #2	$86.94	3.759%	$90.2081	$90.21	$90.20	$90.20
Purchase #3	$72.86	7.418%	$78.2648	$78.26	$78.25	$78.30
Purchase #4	$49.64	5.681%	$52.46	$52.46	$52.45	$52.50
Purchase #5	$151.57	8.312%	$164.1685	$164.17	$164.15	$164.20
Purchase #6	$223.27	10.615%	$246.9701	$246.97	$246.95	$247.00
Purchase #7	$22.52	6.682%	$24.0248	$24.02	$24.00	$24.00
7 purchase totals =	$822.34		$880.9390	$880.93	$880.85	$881.00