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	$107.30	6.805%	$114.6018	$114.60	$114.60	$114.60
Purchase #2	$20.84	5.326%	$21.9499	$21.95	$21.95	$21.90
Purchase #3	$215.81	12.255%	$242.2575	$242.26	$242.25	$242.30
Purchase #4	$147.81	7.183%	$158.4272	$158.43	$158.45	$158.40
Purchase #5	$55.41	11.174%	$61.6015	$61.60	$61.60	$61.60
Purchase #6	$39.93	7.339%	$42.8605	$42.86	$42.85	$42.90
Purchase #7	$32.61	6.451%	$34.7137	$34.71	$34.70	$34.70
7 purchase totals =	$619.71		$676.4121	$676.41	$676.40	$676.40