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	$106.97	4.535%	$111.8211	$111.82	$111.80	$111.80
Purchase #2	$48.67	5.818%	$51.5016	$51.50	$51.50	$51.50
Purchase #3	$165.88	3.366%	$171.4635	$171.46	$171.45	$171.50
Purchase #4	$44.99	5.552%	$47.4878	$47.49	$47.50	$47.50
Purchase #5	$46.42	6.633%	$49.499	$49.50	$49.50	$49.50
Purchase #6	$244.31	13.873%	$278.2031	$278.20	$278.20	$278.20
Purchase #7	$108.76	13.431%	$123.3676	$123.37	$123.35	$123.40
7 purchase totals =	$766.00		$833.3437	$833.34	$833.30	$833.40