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	$69.45	12.863%	$78.3834	$78.38	$78.40	$78.40
Purchase #2	$194.63	9.131%	$212.4017	$212.40	$212.40	$212.40
Purchase #3	$27.76	13.675%	$31.5562	$31.56	$31.55	$31.60
Purchase #4	$75.36	4.419%	$78.6902	$78.69	$78.70	$78.70
Purchase #5	$43.25	9.856%	$47.5127	$47.51	$47.50	$47.50
Purchase #6	$143.92	7.760%	$155.0882	$155.09	$155.10	$155.10
Purchase #7	$109.72	7.169%	$117.5858	$117.59	$117.60	$117.60
7 purchase totals =	$664.09		$721.2182	$721.22	$721.25	$721.30