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	$96.84	9.366%	$105.91	$105.91	$105.90	$105.90
Purchase #2	$202.64	10.358%	$223.6295	$223.63	$223.65	$223.60
Purchase #3	$63.70	11.122%	$70.7847	$70.78	$70.80	$70.80
Purchase #4	$151.41	4.613%	$158.3945	$158.39	$158.40	$158.40
Purchase #5	$57.27	11.439%	$63.8211	$63.82	$63.80	$63.80
Purchase #6	$248.39	7.462%	$266.9249	$266.92	$266.90	$266.90
Purchase #7	$155.55	8.244%	$168.3735	$168.37	$168.35	$168.40
7 purchase totals =	$975.80		$1,057.8382	$1,057.82	$1,057.80	$1,057.80