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	$147.31	11.508%	$164.2624	$164.26	$164.25	$164.30
Purchase #2	$40.55	4.328%	$42.305	$42.31	$42.30	$42.30
Purchase #3	$90.94	10.512%	$100.4996	$100.50	$100.50	$100.50
Purchase #4	$53.26	13.808%	$60.6141	$60.61	$60.60	$60.60
Purchase #5	$107.39	6.193%	$114.0407	$114.04	$114.05	$114.00
Purchase #6	$132.69	13.426%	$150.505	$150.51	$150.50	$150.50
Purchase #7	$114.82	12.869%	$129.5962	$129.60	$129.60	$129.60
7 purchase totals =	$686.96		$761.8230	$761.83	$761.80	$761.80