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	$225.55	5.299%	$237.5019	$237.50	$237.50	$237.50
Purchase #2	$115.82	6.716%	$123.5985	$123.60	$123.60	$123.60
Purchase #3	$142.27	8.547%	$154.4298	$154.43	$154.45	$154.40
Purchase #4	$64.58	4.815%	$67.6895	$67.69	$67.70	$67.70
Purchase #5	$178.62	11.145%	$198.5272	$198.53	$198.55	$198.50
Purchase #6	$147.76	7.172%	$158.3573	$158.36	$158.35	$158.40
Purchase #7	$42.86	8.839%	$46.6484	$46.65	$46.65	$46.60
7 purchase totals =	$917.46		$986.7526	$986.76	$986.80	$986.70