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	$63.89	5.368%	$67.3196	$67.32	$67.30	$67.30
Purchase #2	$131.46	10.545%	$145.3225	$145.32	$145.30	$145.30
Purchase #3	$143.69	5.177%	$151.1288	$151.13	$151.15	$151.10
Purchase #4	$125.84	5.820%	$133.1639	$133.16	$133.15	$133.20
Purchase #5	$54.39	3.774%	$56.4427	$56.44	$56.45	$56.40
Purchase #6	$155.37	12.638%	$175.0057	$175.01	$175.00	$175.00
Purchase #7	$231.77	11.578%	$258.6043	$258.60	$258.60	$258.60
7 purchase totals =	$906.41		$986.9875	$986.98	$986.95	$986.90