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	$185.93	4.583%	$194.4512	$194.45	$194.45	$194.50
Purchase #2	$142.60	9.307%	$155.8718	$155.87	$155.85	$155.90
Purchase #3	$63.86	5.856%	$67.5996	$67.60	$67.60	$67.60
Purchase #4	$35.79	13.447%	$40.6027	$40.60	$40.60	$40.60
Purchase #5	$47.97	13.302%	$54.351	$54.35	$54.35	$54.40
Purchase #6	$74.84	7.612%	$80.5368	$80.54	$80.55	$80.50
Purchase #7	$5.49	13.545%	$6.2336	$6.23	$6.25	$6.20
7 purchase totals =	$556.48		$599.6467	$599.64	$599.65	$599.70