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	$128.45	6.604%	$136.9328	$136.93	$136.95	$136.90
Purchase #2	$76.85	7.447%	$82.573	$82.57	$82.55	$82.60
Purchase #3	$77.35	3.553%	$80.0982	$80.10	$80.10	$80.10
Purchase #4	$111.60	3.137%	$115.1009	$115.10	$115.10	$115.10
Purchase #5	$94.95	10.618%	$105.0318	$105.03	$105.05	$105.00
Purchase #6	$232.61	13.720%	$264.5241	$264.52	$264.50	$264.50
Purchase #7	$101.28	13.854%	$115.3113	$115.31	$115.30	$115.30
7 purchase totals =	$823.09		$899.5721	$899.56	$899.55	$899.50