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	$50.83	6.250%	$54.0069	$54.01	$54.00	$54.00
Purchase #2	$239.78	13.683%	$272.5891	$272.59	$272.60	$272.60
Purchase #3	$99.44	8.223%	$107.617	$107.62	$107.60	$107.60
Purchase #4	$92.55	9.287%	$101.1451	$101.15	$101.15	$101.10
Purchase #5	$69.51	9.470%	$76.0926	$76.09	$76.10	$76.10
Purchase #6	$246.57	10.771%	$273.1281	$273.13	$273.15	$273.10
Purchase #7	$81.51	11.514%	$90.8951	$90.90	$90.90	$90.90
7 purchase totals =	$880.19		$975.4739	$975.49	$975.50	$975.40