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	$200.99	11.212%	$223.525	$223.53	$223.55	$223.50
Purchase #2	$172.80	10.194%	$190.4152	$190.42	$190.40	$190.40
Purchase #3	$92.93	4.196%	$96.8293	$96.83	$96.85	$96.80
Purchase #4	$170.34	9.356%	$186.277	$186.28	$186.30	$186.30
Purchase #5	$92.79	11.783%	$103.7234	$103.72	$103.70	$103.70
Purchase #6	$131.71	8.476%	$142.8737	$142.87	$142.85	$142.90
Purchase #7	$150.98	3.123%	$155.6951	$155.70	$155.70	$155.70
7 purchase totals =	$1,012.54		$1,099.3387	$1,099.35	$1,099.35	$1,099.30