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	$176.45	4.283%	$184.0074	$184.01	$184.00	$184.00
Purchase #2	$58.29	4.789%	$61.0815	$61.08	$61.10	$61.10
Purchase #3	$77.41	4.230%	$80.6844	$80.68	$80.70	$80.70
Purchase #4	$121.77	4.869%	$127.699	$127.70	$127.70	$127.70
Purchase #5	$225.61	13.177%	$255.3386	$255.34	$255.35	$255.30
Purchase #6	$96.69	9.552%	$105.9258	$105.93	$105.95	$105.90
Purchase #7	$230.68	4.659%	$241.4274	$241.43	$241.45	$241.40
7 purchase totals =	$986.90		$1,056.1641	$1,056.17	$1,056.25	$1,056.10