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	$175.52	3.364%	$181.4245	$181.42	$181.40	$181.40
Purchase #2	$241.44	9.697%	$264.8524	$264.85	$264.85	$264.90
Purchase #3	$46.77	11.114%	$51.968	$51.97	$51.95	$52.00
Purchase #4	$126.96	12.772%	$143.1753	$143.18	$143.20	$143.20
Purchase #5	$176.30	11.141%	$195.9416	$195.94	$195.95	$195.90
Purchase #6	$36.85	3.852%	$38.2695	$38.27	$38.25	$38.30
Purchase #7	$199.59	12.614%	$224.7663	$224.77	$224.75	$224.80
7 purchase totals =	$1,003.43		$1,100.3976	$1,100.40	$1,100.35	$1,100.50