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	$183.43	13.462%	$208.1233	$208.12	$208.10	$208.10
Purchase #2	$172.85	4.748%	$181.0569	$181.06	$181.05	$181.10
Purchase #3	$164.96	6.612%	$175.8672	$175.87	$175.85	$175.90
Purchase #4	$233.39	11.697%	$260.6896	$260.69	$260.70	$260.70
Purchase #5	$94.53	9.408%	$103.4234	$103.42	$103.40	$103.40
Purchase #6	$125.82	12.260%	$141.2455	$141.25	$141.25	$141.20
Purchase #7	$233.71	9.354%	$255.5712	$255.57	$255.55	$255.60
7 purchase totals =	$1,208.69		$1,325.9771	$1,325.98	$1,325.90	$1,326.00