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	$235.32	5.442%	$248.1261	$248.13	$248.15	$248.10
Purchase #2	$11.86	5.185%	$12.4749	$12.47	$12.45	$12.50
Purchase #3	$108.87	13.163%	$123.2006	$123.20	$123.20	$123.20
Purchase #4	$250.85	10.335%	$276.7753	$276.78	$276.80	$276.80
Purchase #5	$119.91	9.618%	$131.4429	$131.44	$131.45	$131.40
Purchase #6	$165.37	9.350%	$180.8321	$180.83	$180.85	$180.80
Purchase #7	$37.32	3.500%	$38.6262	$38.63	$38.65	$38.60
7 purchase totals =	$929.50		$1,011.4781	$1,011.48	$1,011.55	$1,011.40