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	$12.71	10.231%	$14.0104	$14.01	$14.00	$14.00
Purchase #2	$48.93	11.244%	$54.4317	$54.43	$54.45	$54.40
Purchase #3	$178.91	8.649%	$194.3839	$194.38	$194.40	$194.40
Purchase #4	$92.34	7.391%	$99.1648	$99.16	$99.15	$99.20
Purchase #5	$139.62	13.842%	$158.9462	$158.95	$158.95	$158.90
Purchase #6	$48.27	6.700%	$51.5041	$51.50	$51.50	$51.50
Purchase #7	$83.26	8.670%	$90.4786	$90.48	$90.50	$90.50
7 purchase totals =	$604.04		$662.9197	$662.91	$662.95	$662.90