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	$89.45	3.327%	$92.426	$92.43	$92.45	$92.40
Purchase #2	$50.83	5.812%	$53.7842	$53.78	$53.80	$53.80
Purchase #3	$132.54	11.838%	$148.2301	$148.23	$148.25	$148.20
Purchase #4	$171.35	3.125%	$176.7047	$176.70	$176.70	$176.70
Purchase #5	$11.39	7.113%	$12.2002	$12.20	$12.20	$12.20
Purchase #6	$83.78	10.488%	$92.5668	$92.57	$92.55	$92.60
Purchase #7	$141.93	10.445%	$156.7546	$156.75	$156.75	$156.80
7 purchase totals =	$681.27		$732.6666	$732.66	$732.70	$732.70