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	$208.93	9.584%	$228.9539	$228.95	$228.95	$229.00
Purchase #2	$55.34	7.702%	$59.6023	$59.60	$59.60	$59.60
Purchase #3	$56.97	4.312%	$59.4265	$59.43	$59.45	$59.40
Purchase #4	$179.56	4.520%	$187.6761	$187.68	$187.70	$187.70
Purchase #5	$181.96	5.541%	$192.0424	$192.04	$192.05	$192.00
Purchase #6	$139.94	3.268%	$144.5132	$144.51	$144.50	$144.50
Purchase #7	$74.58	7.699%	$80.3219	$80.32	$80.30	$80.30
7 purchase totals =	$897.28		$952.5363	$952.53	$952.55	$952.50