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	$226.32	6.798%	$241.7052	$241.71	$241.70	$241.70
Purchase #2	$241.94	13.454%	$274.4906	$274.49	$274.50	$274.50
Purchase #3	$48.59	7.852%	$52.4053	$52.41	$52.40	$52.40
Purchase #4	$98.95	12.769%	$111.5849	$111.58	$111.60	$111.60
Purchase #5	$72.54	5.635%	$76.6276	$76.63	$76.65	$76.60
Purchase #6	$45.72	4.222%	$47.6503	$47.65	$47.65	$47.70
Purchase #7	$170.52	5.836%	$180.4715	$180.47	$180.45	$180.50
7 purchase totals =	$904.58		$984.9354	$984.94	$984.95	$985.00