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	$53.94	10.478%	$59.5918	$59.59	$59.60	$59.60
Purchase #2	$236.64	13.597%	$268.8159	$268.82	$268.80	$268.80
Purchase #3	$120.64	4.469%	$126.0314	$126.03	$126.05	$126.00
Purchase #4	$231.54	10.275%	$255.3307	$255.33	$255.35	$255.30
Purchase #5	$208.57	11.634%	$232.835	$232.84	$232.85	$232.80
Purchase #6	$217.77	7.233%	$233.5213	$233.52	$233.50	$233.50
Purchase #7	$167.54	11.347%	$186.5508	$186.55	$186.55	$186.60
7 purchase totals =	$1,236.64		$1,362.6769	$1,362.68	$1,362.70	$1,362.60