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	$92.89	9.440%	$101.6588	$101.66	$101.65	$101.70
Purchase #2	$176.81	7.660%	$190.3536	$190.35	$190.35	$190.40
Purchase #3	$151.25	11.693%	$168.9357	$168.94	$168.95	$168.90
Purchase #4	$158.91	12.139%	$178.2001	$178.20	$178.20	$178.20
Purchase #5	$154.38	4.820%	$161.8211	$161.82	$161.80	$161.80
Purchase #6	$250.84	4.417%	$261.9196	$261.92	$261.90	$261.90
Purchase #7	$181.37	6.337%	$192.8634	$192.86	$192.85	$192.90
7 purchase totals =	$1,166.45		$1,255.7523	$1,255.75	$1,255.70	$1,255.80