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	$119.68	10.511%	$132.2596	$132.26	$132.25	$132.30
Purchase #2	$209.94	13.730%	$238.7648	$238.76	$238.75	$238.80
Purchase #3	$20.51	7.321%	$22.0115	$22.01	$22.00	$22.00
Purchase #4	$98.46	5.187%	$103.5671	$103.57	$103.55	$103.60
Purchase #5	$170.59	8.747%	$185.5115	$185.51	$185.50	$185.50
Purchase #6	$14.33	12.354%	$16.1003	$16.10	$16.10	$16.10
Purchase #7	$66.59	9.518%	$72.928	$72.93	$72.95	$72.90
7 purchase totals =	$700.10		$771.1428	$771.14	$771.10	$771.20