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	$109.64	8.523%	$118.9846	$118.98	$119.00	$119.00
Purchase #2	$159.45	10.824%	$176.7089	$176.71	$176.70	$176.70
Purchase #3	$48.97	5.207%	$51.5199	$51.52	$51.50	$51.50
Purchase #4	$134.34	3.648%	$139.2407	$139.24	$139.25	$139.20
Purchase #5	$189.42	13.355%	$214.717	$214.72	$214.70	$214.70
Purchase #6	$155.33	6.798%	$165.8893	$165.89	$165.90	$165.90
Purchase #7	$75.81	3.664%	$78.5877	$78.59	$78.60	$78.60
7 purchase totals =	$872.96		$945.6481	$945.65	$945.65	$945.60