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	$105.58	8.818%	$114.89	$114.89	$114.90	$114.90
Purchase #2	$73.36	7.452%	$78.8268	$78.83	$78.85	$78.80
Purchase #3	$207.36	10.852%	$229.8627	$229.86	$229.85	$229.90
Purchase #4	$102.59	13.699%	$116.6438	$116.64	$116.65	$116.60
Purchase #5	$136.61	5.143%	$143.6359	$143.64	$143.65	$143.60
Purchase #6	$43.93	9.443%	$48.0783	$48.08	$48.10	$48.10
Purchase #7	$81.26	4.616%	$85.011	$85.01	$85.00	$85.00
7 purchase totals =	$750.69		$816.9485	$816.95	$817.00	$816.90