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	$122.81	9.614%	$134.617	$134.62	$134.60	$134.60
Purchase #2	$87.67	12.811%	$98.9014	$98.90	$98.90	$98.90
Purchase #3	$247.61	13.336%	$280.6313	$280.63	$280.65	$280.60
Purchase #4	$68.84	13.794%	$78.3358	$78.34	$78.35	$78.30
Purchase #5	$19.49	12.500%	$21.9263	$21.93	$21.95	$21.90
Purchase #6	$198.48	5.410%	$209.2178	$209.22	$209.20	$209.20
Purchase #7	$184.93	5.767%	$195.5949	$195.59	$195.60	$195.60
7 purchase totals =	$929.83		$1,019.2245	$1,019.23	$1,019.25	$1,019.10