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	$43.89	10.712%	$48.5915	$48.59	$48.60	$48.60
Purchase #2	$39.86	11.169%	$44.312	$44.31	$44.30	$44.30
Purchase #3	$200.65	10.764%	$222.248	$222.25	$222.25	$222.20
Purchase #4	$70.78	11.282%	$78.7654	$78.77	$78.75	$78.80
Purchase #5	$57.95	13.698%	$65.888	$65.89	$65.90	$65.90
Purchase #6	$117.37	12.406%	$131.9309	$131.93	$131.95	$131.90
Purchase #7	$223.67	12.546%	$251.7316	$251.73	$251.75	$251.70
7 purchase totals =	$754.17		$843.4674	$843.47	$843.50	$843.40