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	$145.96	3.423%	$150.9562	$150.96	$150.95	$151.00
Purchase #2	$209.39	9.784%	$229.8767	$229.88	$229.90	$229.90
Purchase #3	$35.86	12.228%	$40.245	$40.25	$40.25	$40.20
Purchase #4	$69.94	11.856%	$78.2321	$78.23	$78.25	$78.20
Purchase #5	$184.82	7.500%	$198.6815	$198.68	$198.70	$198.70
Purchase #6	$132.90	9.533%	$145.5694	$145.57	$145.55	$145.60
Purchase #7	$180.27	12.652%	$203.0778	$203.08	$203.10	$203.10
7 purchase totals =	$959.14		$1,046.6387	$1,046.65	$1,046.70	$1,046.70