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	$130.58	9.528%	$143.0217	$143.02	$143.00	$143.00
Purchase #2	$91.63	10.814%	$101.5389	$101.54	$101.55	$101.50
Purchase #3	$238.26	7.278%	$255.6006	$255.60	$255.60	$255.60
Purchase #4	$190.89	10.803%	$211.5118	$211.51	$211.50	$211.50
Purchase #5	$76.73	5.575%	$81.0077	$81.01	$81.00	$81.00
Purchase #6	$164.70	13.203%	$186.4453	$186.45	$186.45	$186.40
Purchase #7	$65.46	7.671%	$70.4814	$70.48	$70.50	$70.50
7 purchase totals =	$958.25		$1,049.6074	$1,049.61	$1,049.60	$1,049.50