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	$225.89	8.667%	$245.4679	$245.47	$245.45	$245.50
Purchase #2	$140.85	8.522%	$152.8532	$152.85	$152.85	$152.90
Purchase #3	$244.30	11.852%	$273.2544	$273.25	$273.25	$273.30
Purchase #4	$169.35	4.262%	$176.5677	$176.57	$176.55	$176.60
Purchase #5	$121.93	5.388%	$128.4996	$128.50	$128.50	$128.50
Purchase #6	$132.26	13.120%	$149.6125	$149.61	$149.60	$149.60
Purchase #7	$105.66	3.619%	$109.4838	$109.48	$109.50	$109.50
7 purchase totals =	$1,140.24		$1,235.7391	$1,235.73	$1,235.70	$1,235.90