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	$244.64	5.230%	$257.4347	$257.43	$257.45	$257.40
Purchase #2	$151.41	3.243%	$156.3202	$156.32	$156.30	$156.30
Purchase #3	$24.32	4.813%	$25.4905	$25.49	$25.50	$25.50
Purchase #4	$37.95	9.549%	$41.5738	$41.57	$41.55	$41.60
Purchase #5	$39.52	3.124%	$40.7546	$40.75	$40.75	$40.80
Purchase #6	$202.84	4.452%	$211.8704	$211.87	$211.85	$211.90
Purchase #7	$186.79	6.783%	$199.46	$199.46	$199.45	$199.50
7 purchase totals =	$887.47		$932.9042	$932.89	$932.85	$933.00