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	$13.42	3.867%	$13.939	$13.94	$13.95	$13.90
Purchase #2	$43.43	12.568%	$48.8883	$48.89	$48.90	$48.90
Purchase #3	$84.96	11.209%	$94.4832	$94.48	$94.50	$94.50
Purchase #4	$157.64	11.392%	$175.5983	$175.60	$175.60	$175.60
Purchase #5	$159.39	5.770%	$168.5868	$168.59	$168.60	$168.60
Purchase #6	$216.54	13.512%	$245.7989	$245.80	$245.80	$245.80
Purchase #7	$40.75	6.545%	$43.4171	$43.42	$43.40	$43.40
7 purchase totals =	$716.13		$790.7116	$790.72	$790.75	$790.70