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	$198.75	7.838%	$214.328	$214.33	$214.35	$214.30
Purchase #2	$93.40	13.146%	$105.6784	$105.68	$105.70	$105.70
Purchase #3	$185.85	13.660%	$211.2371	$211.24	$211.25	$211.20
Purchase #4	$158.31	11.599%	$176.6724	$176.67	$176.65	$176.70
Purchase #5	$150.95	9.359%	$165.0774	$165.08	$165.10	$165.10
Purchase #6	$39.27	6.841%	$41.9565	$41.96	$41.95	$42.00
Purchase #7	$84.79	7.231%	$90.9212	$90.92	$90.90	$90.90
7 purchase totals =	$911.32		$1,005.8710	$1,005.88	$1,005.90	$1,005.90