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	$86.95	11.116%	$96.6154	$96.62	$96.60	$96.60
Purchase #2	$163.58	7.785%	$176.3147	$176.31	$176.30	$176.30
Purchase #3	$14.27	8.693%	$15.5105	$15.51	$15.50	$15.50
Purchase #4	$176.46	12.688%	$198.8492	$198.85	$198.85	$198.80
Purchase #5	$143.89	10.215%	$158.5884	$158.59	$158.60	$158.60
Purchase #6	$137.29	3.128%	$141.5844	$141.58	$141.60	$141.60
Purchase #7	$190.33	4.848%	$199.5572	$199.56	$199.55	$199.60
7 purchase totals =	$912.77		$987.0198	$987.02	$987.00	$987.00