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	$43.62	4.636%	$45.6422	$45.64	$45.65	$45.60
Purchase #2	$210.46	6.158%	$223.4201	$223.42	$223.40	$223.40
Purchase #3	$122.68	12.405%	$137.8985	$137.90	$137.90	$137.90
Purchase #4	$120.64	10.565%	$133.3856	$133.39	$133.40	$133.40
Purchase #5	$56.43	6.749%	$60.2385	$60.24	$60.25	$60.20
Purchase #6	$129.99	10.217%	$143.2711	$143.27	$143.25	$143.30
Purchase #7	$36.98	9.579%	$40.5223	$40.52	$40.50	$40.50
7 purchase totals =	$720.80		$784.3783	$784.38	$784.35	$784.30