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	$214.70	12.726%	$242.0227	$242.02	$242.00	$242.00
Purchase #2	$126.85	3.652%	$131.4826	$131.48	$131.50	$131.50
Purchase #3	$165.95	10.435%	$183.2669	$183.27	$183.25	$183.30
Purchase #4	$23.77	7.807%	$25.6257	$25.63	$25.65	$25.60
Purchase #5	$231.32	10.553%	$255.7312	$255.73	$255.75	$255.70
Purchase #6	$102.95	7.849%	$111.0305	$111.03	$111.05	$111.00
Purchase #7	$153.75	11.139%	$170.8762	$170.88	$170.90	$170.90
7 purchase totals =	$1,019.29		$1,120.0358	$1,120.04	$1,120.10	$1,120.00