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	$137.31	9.789%	$150.7513	$150.75	$150.75	$150.80
Purchase #2	$150.94	9.783%	$165.7065	$165.71	$165.70	$165.70
Purchase #3	$98.97	8.108%	$106.9945	$106.99	$107.00	$107.00
Purchase #4	$39.31	6.473%	$41.8545	$41.85	$41.85	$41.90
Purchase #5	$59.31	8.157%	$64.1479	$64.15	$64.15	$64.10
Purchase #6	$135.93	9.105%	$148.3064	$148.31	$148.30	$148.30
Purchase #7	$70.96	10.639%	$78.5094	$78.51	$78.50	$78.50
7 purchase totals =	$692.73		$756.2705	$756.27	$756.25	$756.30