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	$103.88	5.348%	$109.4355	$109.44	$109.45	$109.40
Purchase #2	$11.76	4.553%	$12.2954	$12.30	$12.30	$12.30
Purchase #3	$113.57	8.482%	$123.203	$123.20	$123.20	$123.20
Purchase #4	$246.32	13.533%	$279.6545	$279.65	$279.65	$279.70
Purchase #5	$96.85	6.418%	$103.0658	$103.07	$103.05	$103.10
Purchase #6	$231.35	10.787%	$256.3057	$256.31	$256.30	$256.30
Purchase #7	$134.83	3.711%	$139.8335	$139.83	$139.85	$139.80
7 purchase totals =	$938.56		$1,023.7934	$1,023.80	$1,023.80	$1,023.80