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	$109.94	12.254%	$123.412	$123.41	$123.40	$123.40
Purchase #2	$51.84	13.534%	$58.856	$58.86	$58.85	$58.90
Purchase #3	$111.46	5.671%	$117.7809	$117.78	$117.80	$117.80
Purchase #4	$169.33	6.228%	$179.8759	$179.88	$179.90	$179.90
Purchase #5	$131.60	12.683%	$148.2908	$148.29	$148.30	$148.30
Purchase #6	$250.25	10.392%	$276.256	$276.26	$276.25	$276.30
Purchase #7	$156.65	5.426%	$165.1498	$165.15	$165.15	$165.10
7 purchase totals =	$981.07		$1,069.6214	$1,069.63	$1,069.65	$1,069.70