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	$78.25	9.661%	$85.8097	$85.81	$85.80	$85.80
Purchase #2	$174.83	5.824%	$185.0121	$185.01	$185.00	$185.00
Purchase #3	$153.38	11.838%	$171.5371	$171.54	$171.55	$171.50
Purchase #4	$95.51	3.546%	$98.8968	$98.90	$98.90	$98.90
Purchase #5	$157.44	4.297%	$164.2052	$164.21	$164.20	$164.20
Purchase #6	$186.84	11.682%	$208.6666	$208.67	$208.65	$208.70
Purchase #7	$62.42	6.196%	$66.2875	$66.29	$66.30	$66.30
7 purchase totals =	$908.67		$980.4150	$980.43	$980.40	$980.40